v international symposium on strong nonlinear … · phonon interference and energy transport in...

V INTERNATIONAL

SYMPOSIUM ON

STRONG

NONLINEAR

VIBRONIC AND

ELECTRONIC

INTERACTIONS

IN SOLIDS

MAY 1-3 , 2015

TARTU, ESTONIA

Max B

InstitutPlanck Inst

Brandenburg

S

e of Physictitute for Sog University

Supported b

cs, Universitlid State Rey of Techno

by

ty of Tartu, esearch, Stuology, Cottb

Estonia uttgart, Gerus, German

rmany ny

V International Symposium on Strong Nonlinear Vibronic and

Electronic Interactions in Solids

PROGRAM

&

BOOK OF ABSTRACTS

Institute of Physics University of Tartu Ravila 14c 50411 Tartu Estonia This document is available online at: http://ttl.ut.ee/ws15/book-of-abstracts.pdf May 2015

SNVE2015, May 1-3, 2015, Tartu, Estonia

2 General Information

Table of Contents

General Information .............................................................................................. 2 Conference history and scope ......................................................................... 2 Topics of the Workshop ................................................................................... 2 Organizing Committee ..................................................................................... 2

Practical Hints ....................................................................................................... 3 Registration ..................................................................................................... 3 Conference site ............................................................................................... 3 Oral presentations ........................................................................................... 3 Posters ............................................................................................................ 3 Internet access ................................................................................................ 3 Conference dinner ........................................................................................... 3

Program ................................................................................................................ 4 List of Posters ....................................................................................................... 7 In memoriam ......................................................................................................... 9 Oral Presentations: Abstracts .............................................................................. 10 Posters: Abstracts ............................................................................................... 52 Author index ........................................................................................................ 79 Timetable ............................................................................................................ 82

General Information

Conference history and scope

Over the past decades an intense collaboration between Estonian and German researchers has developed in the field of condensed matter physics, reflected by the organization of a series of bilateral Estonian-German workshops in 2008, 2009, and 2011. From 2013 the bilateral format of the meetings has developed into an international scientific workshop on current topics in condensed matter physics and a special focus on nonlinear phenomena. In order to keep the workshop compact and its topics focused on the chosen problems, it is supposed that the number of participants will be limited and the participants will have to be invited / approved by the Organizing Committee. Topics of the Workshop

Nonlinear dynamics of crystal lattices Strongly correlated electronic and magnetic systems Solid state spectroscopy and nonlinear quantum optics

Organizing Committee

Vladimir Hizhnyakov (Institute of Physics, University of Tartu, Estonia) Reinhard K. Kremer (Max Planck Institute, Stuttgart, Germany) Götz Seibold (Brandenburg Technical University, Cottbus, Germany)


3 Practical Hints

Practical Hints

Registration

Welcome reception and early registration will be on April 30 at 19:00-21:00, at University Café in Ülikooli 20. Regular registration will take place on Day 1 of the conference. Conference site

All lectures are held in the Dorpat Conference Centre, which is located on the 4th floor of the Tasku Centre in Turu 2. The registration and sessions will take place in the Peterson Hall of the Conference Centre. Lunch and coffee breaks will be organized near the lecture rooms. Oral presentations

The duration of oral presentation is set to 22 min plus 3 min for discussion. We wish to avoid the use of participants' laptops for presentation that usually leads to a waste of time. Rather hand a flash with the file of your presentation to organizers. This can be done during the coffee break before your talk. The file will be copied on our laptop connected to an LCD projector. Types for the presentation files are MS PowerPoint and Adobe Acrobat, the latter is preferable. In the lecture hall, there will be also a whiteboard with color markers. Posters

The posters can be put up on their respective boards after lunch on Friday and removed after the presentation. Stands for poster presentations are of A0 format. Posters can be fastened to them by paperclips, which will be provided by organizers. Internet access

Wireless internet access is available in the conference rooms. Conference dinner

Banquet will start on May 2 at 19:00 in the Dorpat restaurant.


4 Program

Program

Thursday, April 30, 2015

19:00 - 21:00 Welcome reception and early registration

Friday, May 1, 2015

08:00 - 09:00 Registration 09:00 - 09:10 Welcome 09:10 - 09:20 In memoriam: Ernst Sigmund

1st Session: Lattice dynamics

09:20 - 09:45 A. Bussmann-Holder. Tiny cause with huge impact: polar instability through strong magneto-electric-elastic coupling in bulk EuTiO3 (O01)

09:45 - 10:10 F.M. Russell. Tracks in mica: new perspectives (O02) 10:10 - 10:35 B. Tsukerblat. Microscopic theory of spin-crossover in solids:

interaction with local modes and phonons (O03) 10:35 - 11:00 J.F.R. Archilla. Experimental observation of intrinsic localized

modes in germanium (O04) 11:00 - 11:20 Coffee break

2nd Session: Strong correlations

11:20 - 11:45 J. van den Brink. Resonant inelastic X-ray scattering on high-Tc cuprates and magnetic iridates (O05)

11:45 - 12:10 R.K. Kremer. Tuning the properties of quantum chain magnets by hydrostatic pressure (O06)

12:10 - 12:35 R. Stern. Han purple - frustration removed (O07) 12:35 - 13:00 B. Büchner. NMR studies of nanoscale electronic order in high

temperature superconductors (O08) 13:00 - 14:00 Lunch

3rd Session: Superconductivity

14:00 - 14:25 A. Bianconi. Superconductivity driven by shape resonances between quasi localized pairs and delocalized pairs (O09)

14:25 - 14:50 J. Lorenzana. Coherent control of lattice and superconductivity by impulsive stimulated Raman scattering (O10)

14:50 - 15:15 A. Mann. Coherent fluctuation spectroscopy in cuprates (O11) 15:15 - 15:40 M. Silaev. Resistive and thermoelectric signatures of time-reversal

symmetry breaking states in multiband superconductors (O12) 15:40 - 16:00 Coffee break

4th Session: Lattice dynamics


5 Program

16:00 - 16:25 S.M.M. Coelho. The introduction of subthreshold induced defects in germanium by above threshold radiation exposure (O13)

16:25 - 16:50 E. Heinsalu. The dynamics of dimers and dipoles on a surface (O14)

16:50 - 17:15 G.M. Chechin. Ab initio simulations of discrete breathers in graphane and deformed graphene (O15)

17:15 - 17:40 S. Uhlig. Self-organized surface structures produced by ultrafast white-light supercontinuum (O16)

17:40 - 18:00 J. Kalda. Methods of statistical topography for revealing anomalous long-range correlations in disordered media (O17)

18:00 - 19:30 POSTER SESSION

Saturday, May 2, 2015

5th Session: Strong correlations

09:00 - 09:25 S.G. Ovchinnikov. Doping dependent band structure and pairing in strongly correlated electron systems of high-Tc cuprates (O18)

09:25 - 09:50 A.V. Mikheyenkov. Elementary excitations in the symmetric spin-orbital model (O19)

09:50 - 10:15 S.V. Nikolaev. Electronic structure of the Hubbard and t-J models within the cluster perturbation theory in the X-operators representation (O20)

10:15 - 10:40 G. Seibold. Static and dynamical correlations of strongly disordered superconductors (O21)

10:40 - 11:00 Coffee break


11:00 - 11:25 F. Piazza. Nonlinear localized modes in biomolecular structures (O22)

11:25 - 11:50 W. Brenig. Get your conductivity the typical way (O23) 11:50 - 12:15 V.I. Dubinko. Effect of discrete breathers on the rate of chemical

and nuclear reactions in solids (O24) 12:15 - 12:40 M. Patriarca. Numerical experiments of dislocation nucleation

(O25) 12:40 - 14:00 Lunch


14:00 - 14:25 S.V. Dmitriev. Discrete breathers in metals and ordered alloys (O26)

14:25 - 14:50 S.A. Shcherbinin. On the theory of exact interactions between vibrational modes in physical systems with discrete symmetry (O27)

14:50 - 15:15 Y.A. Kosevich. Phonon interference and energy transport in nonlinear lattices with resonance defects (O28)


6 Program

15:15 - 15:40 M. Letz. Mechanism of dielectric loss in glass ceramics for microwave electronics (O29)

15:40 - 16:00 Coffee break

8th Session: Strong correlations

16:00 - 16:25 J. Röhler. Nonlinearily doped cuprate superconductors (O30) 16:25 - 16:50 M. Rübhausen. Time resolved Raman scattering and VUV

spectroscopy to study correlated oxides (O31) 16:50 - 17:15 I.A. Makarov. Polaronic effects in the strongly-correlated systems

with strong electron-phonon interaction (O32) 17:15 - 17:40 A.A. Tsirlin. Unconventional ferrimagnetism of spin-1/2 kagome

francisites Cu3Bi(SeO3)2O2X (X = Cl, Br) (O33)

19:00 BANQUET

Sunday, May 3, 2015

9th Session: Strong interactions

09:00 - 09:25 V. Yudson. One-dimensional electrons and photons: effects of interaction with two-level systems (O34)

09:25 - 09:50 I. Heinmaa. Local structure of spin Peierls compound TiPO4: 45/47Ti

and 31P NMR study (O35) 09:50 - 10:15 G. Litak. Superconductivity in a multi-orbital Hubbard model (O36) 10:15 - 10:40 A. Gabovich. Competition between d-wave superconductivity and

charge density waves: energy gaps and tunneling (O37) 10:40 - 11:00 Coffee break

10th Session: Strong interactions

11:00 - 11:25 T. Rõõm. Magnetic field induced directional dichroism of THz light (O38)

11:25 - 11:50 D. Hüvonen. Magnetic field induced ordering in clean and bond disordered quantum magnet DTN: neutron scattering and THz optical study (O39)

11:50 - 12:15 E.A. Karatsuba. On the method of evaluation of characteristics of quantum packets in the Jaynes-Cummings model (O40)

12:15 - 12:40 A. Shugai. Rotations and vibrations of water molecule inside the fullerene cage: infrared study of H2O@C60 (O41)

12:40 - 12:50 Closing


7 List of Posters

List of Posters

Lattice dynamics

P01 A.Pishtshev, P.Rubin, M.Klopov. Covalency, electron localization and latticedynamicscontrolledbypolarizationeffectsinthenarrow‐gapsystemFeAs2

P02 K.Pae. Quantumfrictionofpseudo‐rotationincaseofEe‐problem P03 M.Haas,A.Shelkan. Aboutmobileself‐localizedvibrations(ILM)incrystallatticesP04 V.Krasnenko,V.Boltrushko. Boundstatesofbenzene,graphene,carbonnanotubes

andfullerenes:distortions,inducedbypseudo‐Jahn‐TellereffectP05 V.Krasnenko, A.Tamm, V.Boltrushko, A.‐Li.Peikolainen, J.Kozlova, K.Kukli,

V.Hizhnyakov. Modellingofcarbonnanoparticlesabsorbedongraphene P06 B.Ducharne, G.Sebald, D.Guyomar, G.Litak. Dynamics of magnetic field

penetrationintotheconductingmagnetP07 M.Klopov, A.Shelkan, V.Hizhnyakov. Transverse intrinsicpseudo‐localmodes in

monatomicchainandgraphene

Strong correlations

P08 A.Sherman. TheHubbardmodelinstrongmagneticfield:low‐frequencyquantumoscillationsduetostrongelectroncorrelations

P09 E.I.Shneyder, S.G.Ovchinnikov, A.A.Kordyuk. Peculiarities of the angle‐resolvedphotoemissionlineshapeanalysisforstronglycorrelatedelectronsystems

P10 P.Rubin, A.Sherman, M.Schreiber. The spin‐1 J1‐J3 Heisenberg model on atriangularlattice

P11 E.vonOelsen, G.Seibold. Electron dynamics and inhomogeneous quantumquenches–overcomingthesmall‐amplitudelimit

P12 A.Sherman. Strong‐couplingdiagramtechniqueforstrongcorrelations P13 A.Leitmäe, I.Heinmaa, E.Joon, A.A.Tsirlin, R.Stern. 47,49Ti NMR study of spin‐

PeierlscompoundTiPO4

Superconductivity

P14 A.Vargunin, T.Örd. Shrinking of the fluctuation region in a two‐bandsuperconductor

P15 N.Kristoffel,P.Rubin. MultibandsuperconductivitywithdifferentpairconstituentsP16 T.Örd,K.Rägo,A.Vargunin,G.Litak. Temperaturedependent sizesof theCooper

pairsinaBCS‐typetwo‐bandsuperconductor

Optics

P17 A.Loot. Leakysurfaceplasmonpolaritons P18 I.Rebane. Timedependenttheoryoftwostepabsorptionoftwopulses P19 T.Vaikjärv. Optical manifestations of energy relaxation in quasi‐degenerate

electronicstates P20 J.Viirok. DirectionaldichroismofTHzradiationinmultiferroicSr2CoSi2O7


8 List of Posters

P21 I.Tehver,G.Benedek,V.Hizhnyakov. Fermiexcitationsindopedhelium‐3dropletsprobedbyRamanscattering

P22 V.Hizhnyakov, A.Loot, S.Ch.Azizabadi. Resonantly enhanced dynamical Casimireffectforsurfaceplasmonpolaritonsandforguidedwaves

P23 V.Palm, A.Loot, M.Rähn, J.Jäme, V.Hizhnyakov. Light propagation in metal‐coatedSNOMtips:experimentandnumericalsimulations

P24 P.Konsin, B.Sorkin. Semi‐microscopic theory of thickness dependences of theforbidden (optical) gap and of the refractive index in PMMA type systemswithstructuralorderingpolargroups

P25 R.Laasner,V.Nagirnyi,S.Vielhauer,V.Sirutkaitis,R.Grigonis. Modelofband tailabsorptionsaturationwithfspulses

P26 V.G.Fedoseyev. SurfacetransverseAbrahamforceexertedonavortexwavepacketduringitsreflectionandrefractionataplaneinterface

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Oral Presentations:

Abstracts

FRIDAY


11 O01 Oral Presentations: Abstracts

Tiny cause with huge impact: polar instability through strong magneto-electric-elastic coupling in bulk EuTiO3

A. Bussmann-Holder*, P. Reuvekamp, K. Caslin, R.K. Kremer, J. Köhler

Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany * [email protected]

Multiferroic materials with combined polar, magnetic, and elastic orderings are at the forefront of scientific research in view of their multiple interactive couplings: magnetic order can be tuned by strain and an electric field, polar order can be triggered by a magnetic field and strain, and elastic properties are controlled by a magnetic and/or an electric field. Such materials are desirable for multiple applications. Even though the phenomenon of multiferroicity has been predicted long ago [1], its realization remains rare for rather simple reasons: typically polar order is achieved when a transition metal d0 configuration is combined with highly polarizable anions, whereas magnetic order relies on a finite dn configuration. Obviously these two requirements yield a certain incompatibility of the coexistence of the two phenomena which have been tried to overcome by combining magnetic layers with polar ones, by growing composites, and via strain engineering [2, 3]. Even though a rather large number of materials have been shown to exhibit the desired properties, the coupling between magnetic and polar order is either very weak, or the spontaneous polarization/magnetization appears at low temperature only and remains too small to be of technological interest. Here we propose a new strategy to achieve strong magnetic-polar coupling by deriving the soft mode frequency of EuTiO3 as a function of its lattice parameters which exhibits unusual, yet very small temperature dependencies at high and low temperatures [4, 5]. Specifically we develop a route of how to induce ferroelectric order in bulk EuTiO3 (ETO) by combining experimental results with theoretical concepts. We show that marginal changes in the lattice parameter of the order of 0.01% have a more than 1000% effect on the transverse optic soft mode of ETO and thus easily induce a ferroelectric instability.

1. Smolenskii, G. A., Isupov, V. A., & Agronovskaya, A. I., Sov. Phys Solid State, 1, 149 (1959). 2. Erenstein, W., Mathur, N. D., & Scott, J. F., Nature 422, 759-765 (2006). 3. Ramesh, R., & Spaldin, N. A., Nature Materials 6, 21 (2007). 4. Reuvekamp, P. G., Kremer, R. K., Köhler, J., & Bussmann-Holder, A., Phys. Rev. B 90,

094420 (2014). 5. Reuvekamp, P. G., Kremer, R. K., Köhler, J., & Bussmann-Holder, Phys. Rev. B 90, 104105

(2014).

FRIDAY


12 Oral Presentations: Abstracts O02

Tracks in mica: new perspectives

F. M. Russell

Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, SA 0002 [email protected]

Crystals of muscovite mica containing an impurity of iron can record the tracks of relativistic charged particles that pass through the crystal shortly after growth from liquid granite deep underground.[1] Muscovite has a layered structure containing monatomic sheets of potassium sandwiched between silicate layers bonded by a complex layer containing Al, O, F and H. The sensitivity for recording tracks of charged leptons exceeds that of photographic film. The recording process, however, is restricted to the (001)-plane of the potassium sheets. While this limits the number of tracks recorded it has the great advantage of permitting detailed measurements on tracks by preventing obscuration by overlying tracks in other spatial directions.[2] The potassium isotope K40 is radioactive with three decay channels, giving electrons, positrons and electron capture. Emission of electrons or positrons causes nuclear recoil and changes the electronic charge of the atom. These decay events allow detailed study of the recording process. The dynamic interaction of the recoil nucleus with the lattice creates a mobile, highly localized excitation of the lattice called a quodon. These non-linear excitations propagate along chains of atoms with most of their energy on just one chain. An outstanding property of quodons, with energies up to tens of eV, is their stability against thermal motions at >900K. The paths of quodons also can be recorded, reaching >400mm in large crystals. It has been shown that after propagating >107 unit cells along a chain in a crystal of muscovite an energetic quodon can eject the last atom.[3] The creation of quodons and emission of electrons and positrons from known lattice sites in the K sheet gives rise to quantum mechanical effects such as diffraction scattering via de Broglie waves. This influences the spatial distribution of the particle tracks. The paths of relativistic muons from neutrino interactions in the Earth show direct evidence for atomic cascades created by nuclear scattering events. These cascades create supersonic kink-like excitations that propagate in the potassium sheets to produce fan-shaped patterns of up to 120mm length. The great range of these fans shows that the kink-excitations must gain energy from the exothermic recording process. In addition to the tracks of muons, the tracks of leptons caused by electron-positron showers and of rare nuclear stars have been identified. Recent studies of the decoration of tracks with the Fe impurity associated with the recording process have led to improvements in understanding the process. The recording process is charge sensitive, responding only to positive charges. The extent of decoration along an initially relativistic positron track increases as it slows, reaching a maximum before the particle comes to rest. This maximum extent of decoration is similar to that measured on the whole length of tracks of quodons. There is no clear evidence for positrons or quodons gaining energy from the recording process. The ejection experiment supports this finding as it was conducted in the absence of the recording process. A possible connection between nonlinear lattice excitations and high Tc superconductors was suggested.[4] The implications of these recent results for coupling of lattice excitations to holes in the layered HTSC compounds is examined.

1. F.M. Russell, “Tracks in mica caused by electron showers”, Nature 216, (1967) 907-909 2. F.M. Russell, “Identification and selection criteria for charged lepton tracks in mica”, Nucl.

Tracks Radiat. Meas. 15, (1988) 41-44 3. F.M. Russell and C. J. Eilbeck, “Evidence for moving breathers is a layered crystal insulator at

300K”, Europhysics Letters, 78,(2007) 10004 4. F.M. Russell and D. R. Collins, “Anharmonic excitations in high Tc materials”, Phys. Letts. A,

216 (1996) 197-202

FRIDAY



Microscopic theory of spin-crossover in solids: interaction with local modes and phonons

A.V. Palii1, S.M. Ostrovsky1, O.S. Reu, B. Tsukerblat2,*, S. Decurtins3, S.X. Liu3, S.I. Klokishner1

1Institute of Applied Physics, Academy of Sciences of Moldova, 2028 Kishinev, Moldova 2Department of Chemistry, Ben-Gurion University, Beer-Sheva, 84105 Israel

3Departement für Chemie und Biochemie, Universität Bern, CH-3012 Bern, Switzerland * [email protected]

It was understood long time ago (Sasaki and Kambara [1]) that the spin-crossover (SCO)

transformation in solids is a cooperative transition between high-spin (hs) and low-spin (ls) states of d4- d7 metal ions coupled via the phonon field. The microscopic theory of SCO have been restricted to the cases of continuous spectra of the phonons (mainly acoustic branches) while SCO occurs mainly in the so-called molecular magnetic materials which exhibit distinct molecular (local) vibrations along with the phonons.

Here we present a microscopic theoretical approach to the description of the SCO phenomenon in solids which takes into account the strong interaction of spin-crossover ions with the molecular modes and a relatively weak coupling with the phonons which mediate intermolecular coupling through the crystal lattice. Since the ligand surrounding of the SCO ions participates both in local and crystal vibrations we use the Hizhnyakov’s et al [2] transformation of the vibrational coordinates and present the electron-vibrational Hamiltonian for a SCO center as a sum of two parts including the strong coupling of the electronic shells with the local vibrations and the interaction between the local vibrations around the SCO center and phonons. Within the mean field approximation the cooperative SCO transition is characterized by the two order parameters: the mean values of the products of electronic matrices and the coordinates of the local modes for the hs and ls states of the SCO complex. Finally, we demonstrate that the approach provides a reasonable description of the observed spin transition in [(Fe(ptz)6](BF4)2 crystal.

(*) S.K., A.P., S.O., O.R. and S.D. gratefully acknowledge financial support from SCOPES (project IZ73ZO_152404/1).

1. N. Sasaki, T. Kambara, “Theory of cooperative high-spin~low-spin transitions in iron (III)

compounds induced by the molecular distortions”, J. Chem. Phys. 74, 3472 (1981); N. Sasaki , T. Kambara, “Theory of the two-step spin conversion induced by the cooperative molecular distortions in spin-crossover compounds”, Phys. Rev. B 40, 2442 (1989).

2. V. Hizhnyakov, K. Pae, T. Vaikjärv, “Optical Jahn–Teller effect in the case of local modes and Phonons”, Chem. Phys. Lett. 525, 64 (2012); K. Pae, V. Hizhnyakov, “Nonadiabaticity in a Jahn-Teller system probed by absorption and resonance Raman scattering”, J. Chem. Phys., 138, 104103 (2013).

FRIDAY



Experimental observation of intrinsic localized modes in germanium

J.F.R. Archilla1,*, S.M.M. Coelho2, F.D. Auret2, V.I. Dubinko3 and V. Hizhnyakov4 1 Group of Nonlinear Physics, Universidad de Sevilla, Avda Reina Mercedes s/n, 41012-Sevilla, Spain

2Department of Physics, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa 3NSC Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine

4Institute of Physics, University of Tartu, Ravila 14c, 50411, Tartu, Estonia * [email protected]

We have found experimentally that very low energy (2-8eV) argon plasma when acting on

a germanium wafer is able to modify or anneal defects at least two microns below the surface. The plasma has a very low flux so each Ar impact is practically isolated in time and space, meaning that it is not possible the formation of a wavefront or shockwave . The sample is kept at approximately room temperature, therefore excluding thermal annealing. There is very little diminution of the rate of annealing with depth, which implies that the perturbation does not spread and keep most of its energy while travelling. The annealing energies of the defects studied are about 1 eV. The conclusion is that localized energy produced by Ar impacts is able to travel long distances through the semiconductor [1]. The most probable cause is vibrational energy in the form of intrinsic localized modes (ILMs). Stationary ILMs have been found in Ge but not yet mobile ones [2].

1. J.F.R. Archilla, S.M.M. Coelho, F.D. Auret, V.I. Dubinko and V. Hizhyakov, "Long range

annealing of defects in germanium by low energy plasma ions?", Physica D 297, 56–61 (2015). 2. V. Hizhnyakov, M. Haas, A. Shelkan, M. Klopov, "Standing and moving discrete breathers with

frequencies above phonon spectrum", in “Quodons in Mica: nonlinear localized travelling excitations in crystals”, Springer, New York (2015), to appear.

FRIDAY



Resonant Inelastic X-ray Scattering on high-Tc cuprates and magnetic iridates

J. van den Brink

Institute for Theoretical Solid State Physics Leibniz Institute for Solid State and Materials Research Dresden

Helmholtzstraße 20, 01069 Dresden, Germany [email protected]

Resonant Inelastic X-ray Scattering (RIXS) provides direct access to elementary charge,

spin and orbital excitations in complex oxides. As a technique it has made tremendous progress with the advent high-brilliance synchrotron X-ray sources. From the theoretical perspective the fundamental question is to precisely which low-energy correlation functions RIXS is sensitive. Depending on the experimental RIXS setup, the measured charge dynamics can include charge-transfer, phonon, d-d and orbital excitations [1]. The focus of this talk will be on RIXS as a probe of spin dynamics and superconducting gap of high-Tc cuprates [2-4] and the combined magnetic and orbital modes in strongly spin-orbit coupled iridium-oxides [5-10].

1. L. J. P. Ament, et al., Rev. Mod. Phys. 83, 705 (2011). 2. L. Braicovich, et al., Phys. Rev. Lett. 104, 077002 (2010). 3. M. P. M. Dean, et al., Nature Materials 11, 850 (2012). 4. P. Marra, et al., Phys. Rev. Lett. 110, 117005 (2013). 5. L. J. P. Ament, et al., Phys. Rev. B 84, 020403 (2011). 6. V. M. Katukuri, et al., Phys. Rev. B 85, 220402 (2012). 7. N. A. Bogdanov, et al., Phys. Rev. B 85, 235147 (2012). 8. J. Kim, et al., Phys. Rev. Lett. 108, 177003 (2012). 9. H. Gretarsson, et al., Phys. Rev. Lett. 110, 076402 (2013). 10. A. Lupascu, et al., Phys. Rev. Lett. 112, 147201 (2014).

FRIDAY



Tuning the magnetic and structural properties of the ferromagnetic quantum-spin chain CuAs2O4 by hydrostatic pressure

K. Caslin1,*, R.K. Kremer1,*, K. Syassen1, M. Hanfland2, M.-H. Whangbo3, E. Gordon3

1Max Planck Institute for Solid State Research, Stuttgart, Germany 2European Synchrotron Radiation Facility, Grenoble, France

3North Carolina State University, U.S.A. * [email protected]

Antiferromagnetic quantum spin chains with competing spin-exchange interactions along the spin chains are known to exhibit unusual groundstates. For example, helicoidal magnetic ordering supporting multiferroic behavior has been found in a numbers of Cu2+ systems (e.g. LiCuVO4, CuCl2, CuBr2) where the next-nearest neighbor (nnn) spin-exchange interaction is antiferromagnetic and larger in magnitude than the ferromagnetic nearest neighbor (nn) spin-exchange interaction. Systems with strong ferromagnetic nn which realize a ferromagnetic groundstate are less frequent. CuAs2O4 (Trippkeite) is a new S=1/2 quantum-spin-chain with dominant nn ferromagnetic spin-exchange which undergoes long-range ferromagnetic ordering below 7.4 K. ab initio calculations indicate a ratio of nearest to next-nearest neighbor spin ex-change interaction of Jnn/Jnnn= – 4.1 which is in the vicinity of the quantum critical point where for classical spins helicoidal order changes to a ferromagnetic groundstate. In order to tune the spin-exchange interactions we have applied hydrostatic pressure and investigated the response in the magnetic and structural properties of CuAs2O4 by single-crystal synchrotron x-ray diffraction, Raman spectroscopy and SQUID magnetometry. Precise structural parameters gained from the single crystal x-ray structure determination under hydrostatic pressure have been utilized for detailed density functional calculations of the spin-exchange interactions. Furthermore, we have correlated the spin-exchange constants to the magnetic properties measured under hydrostatic pressure.

(*) This work is part of the PhD Thesis of K. Caslin, Brock University St. Catharines, Ontario, Canada.

FRIDAY



Han Purple - frustration removed.

R. Stern*, I. Heinmaa, E. Joon, A.A. Tsirlin

National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn, 12618, Estonia [email protected]

FRIDAY



NMR studies of nanoscale electronic order in high temperature superconductors

B. Büchner

Institut für Festkörperforschung, IFW Dresden Institut für Festkörperphysik, TU Dresden

Helmholtzstraße 20, 01069 Dresden, Germany [email protected]

Using a broad spectrum of experimental techniques we have studied the interplay between

structural transition, magnetism, electronic order and superconductivity in several classes of iron pnictide superconductors. In LaO1-xFxAsFe and other 1111 type materials an intimate interplay between structure, magnetism and electronic properties is evident from the phase diagram. Moreover, measurements of the electrical field gradient by NQR yield clear-cut evidence for nanoscale order of charges and/or orbitals. This electronic order develops upon doping and/or temperature and seems to suppress long range magnetic order while our data do not give any evidence for a competition between the electronic order and superconductivity. The iron selenide FeSe is different from other Fe-based superconductors since a structural transition, which is often associated with electronic nematic order, occurs at Ts ~ 90 K without any sign of antiferromagnetism, and it is therefore tempting to conclude that an alternative scenario for nematicity, based on orbital (rather than spin) degrees of freedom, takes place. To establish whether this is indeed the case, we have conducted extensive nuclear magnetic resonance (NMR) measurements on FeSe. Below the nematic transition temperature Ts, we observe a clear splitting of the Se NMR line, which we show to be of electronic origin. Moreover, by measuring the spin-lattice relaxation rate and Knight shift, we establish unequivocally that this line splitting is driven by orbital nematic order. We furthermore establish a connection between orbital nematicity and superconductivity, showing that the two order parameters compete with each other. Intriguingly, this may provide an explanation for the very high superconducting transition temperature reported in the single-layer FeSe.

FRIDAY



Superconductivity driven by shape resonances between quasi localized pairs and delocalized pairs

A. Bianconi1,2 1RICMASS Rome International Center for Materials Science,

Superstripes , Via dei Sabelli 119A, 00185 Rome, Italy; 2INSTM Istituto Nationale di Scienza e Tecnologia dei Materiali

[email protected]

Nanoscale phase separation (NPS) is a universal feature of high temperature

superconductors [1-3]. NPS was observed using fast (10-15 s) and local (1 nm) probes: XANES EXAFS method [4-6] and confirmed by scanning nano x-ray diffraction [3]. The electrons fluctuate between puddles of charge density wave (CDW) phase and the superconducting phase [3]. In the superconducting phase the multiple electronic components form both first a BCS condensate and second polaronic condensate at the BEC-BCS crossover. In this complex landscape new low energy quantum physics emerges on in the intermediate regime where localization and delocalization coexist in different portions of the k-space and real space. The key driving mechanism is the shape resonance in the configuration interaction between closed and open scattering channels that is the key quantum phenomenon which allows quantum fluctuations between pairs of localized and delocalized electrons via exchange interaction [7]. The proximity to a Lifshitz topological transition in presence of quenched disorder can explain both phase separation [7,8] and shape resonances [9]. We propose that high temperature superconductivity emerges where shape resonances dominate in complex system in the intermediate regime where localization and delocalization coexist.

1. V. Hizhyakov, N. Kristoffel, and E. Sigmund, Physica C: Superconductivity 161, 435 (1989),

doi: 10.1016/0921-4534(89)90357-2. 2. A. Bianconi, Int. J. Mod. Phys. B 14, 3289 (2000), doi:10.1142/S0217979200003769. 3. .N. Poccia, et al., Proc. Nat. Acad. Sci. 109, 15685 (2012), doi: 10.1073/pnas.1208492109. 4. A. Bianconi, et al., Chemical Physics Letters 59, 121 (1978) doi:10.1016/0009-2614(78)85629-2. 5. A. Bianconi et al., Phys. Rev. B 44, 10126 (1991), doi: 10.1103/physrevb.44.10126. 6. A. Bianconi et al, Europhys. Lett. 31 411 (1995), doi:10.1209/0295-5075/31/7/012 7. A. Bianconi, Journal of Superconductivity 18, 625 (2005), doi: 10.1007/s10948-005-0047-5. 8. A. Bianconi et al., Supercond. Sci. Technol. 28 024005 (2015), doi:10.1088/0953-

2048/28/2/024005 9. K I Kugel et al, Supercond. Sci. Technol. 22 014007 (2009), doi:10.1088/0953-2048/22/1/014007 10. G. Campi, et al., J. of Supercond. 9, (2015), doi: 10.1007/s10948-015-2955-3.

FRIDAY



Coherent control of lattice and superconductivity by impulsive stimulated Raman scattering

J. Lorenzana1,*, B. Mansart2,3, A. Mann2, A. Odeh3, M. Chergui3, F. Carbone2 1Institute for Complex Systems - CNR and Physics Department, Sapienza, University of Rome, Italy

2Laboratory for Ultrafast Microscopy and Electron Scattering, ICMP, EPFL, CH-1015 Lausanne, Switzerland

3Laboratory of Ultrafast Spectroscopy, ISIC, EPFL, CH-1015 Lausanne, Switzerland * [email protected]

It has been recently demonstrated that a pump pulse can generate coherent charge

fluctuations in a superconductor through a stimulated Raman process [1], paving the way to a new technique, Coherent Charge Fluctuation Spectroscopy, to investigate pairing interactions and manipulate the superconducting wave function. We will present the basic phenomena involved, first using the lattice as a pedagogical example, showing that one can obtain electron phonon matrix elements from these experiments. Generalizing to fluctuations of the superconducting condensate we will show that the technique bears a strong analogy with nuclear magnetic resonance and electron paramagnetic resonance. The reflectivity of the system gets modulated by the coherent oscillations. In the case of the superconductor a resonance at the Mott scale (2.6eV) allows to identify a high-energy excitation which is coupled to the superconducting quasiparticles which suggest that non-retarded interactions are involved in the pairing as requested by unconventional theories of superconductivity.

1. B. Mansart, J. Lorenzana, A. Mann, A. Odeh, M. Scarongella, M. Chergui, F. Carbone, Coupling

of a high-energy excitation to superconducting quasiparticles in a cuprate from coherent charge fluctuation spectroscopy, Proc. Natl. Acad. Sci. USA, 110 4539 (2013)

2. J. Lorenzana, B. Mansart, A. Mann, A. Odeh, M. Chergui, and F. Carbone, Investigating pairing interactions with coherent charge fluctuation spectroscopy, Europ. Phys. J ST 222,1223 (2013)

FRIDAY



Coherent Fluctuation Spectroscopy in Cuprates

A. Mann1,*, E. Baldini1,2, A. Tramontana3, J. Lorenzana3, F.Carbone1 1 Laboratory for Ultrafast Microscopy and Electron Scattering, ICMP, EPFL, CH-1015 Lausanne

2 Laboratory of Ultrafast Spectroscopy, ISIC, EPFL CH-1015 Lausanne 3Institute for Complex Systems - Consiglio Nazionale delle Ricerche, and Physics Department,

University of Rome “La Sapienza”, I-00185 Rome * [email protected]

The understanding of a phenomenon as complex as superconductivity requires very

specific probes. For conventional superconductivity, the key experiment was the stud of the change of transition temperature upon isotope substitution. For the much more complex situation of high-temperature superconductivity, such a clean approach fails due to the strongly correlated nature of the material. However, similar specificity can be achieved by coherently exciting the superconducting condensate and studying its response on the eV scale using a technique called Coherent Charge Fluctuation Spectroscopy. This was demonstrated in optimally doped La2-xSrxCuO4 [1,2].

In this talk, I will explain the experimental realization of such a coherent fluctuation spectroscopy experiment and show that it is possible to use the same principle for coherent lattice vibrations. I will discuss a recent experiment in which a c-axis phonon is coherently excited in the undoped parent compound lanthanum cuprate (La2CuO4) [3], and show that it is possible to quantify electron-phonon matrix elements using CFS. This type of experiment opens up an interesting perspective by giving direct feedback to theory in correlated systems.

1. Mansart et al., Proc. Natl. Acad. Sci. USA 110, 4539–4544 (2013) 2. Lorenzana et al., Eur. Phys. J. Special Topics 222, 1223–1239 (2013) 3. Mann et al., in submission

FRIDAY



Resistive and thermoelectric signatures of time-reversal symmetry breaking states in multiband superconductors

M. Silaev*, J. Garaud, E. Babaev

KTH-Royal Institute of Technology, Stockholm, SE-10691 Sweden * [email protected]

A fundamentally interesting state that can appear in multicomponent superconducting

systems is the so called s+is state. In addition to the usual gauge symmetry U(1), it is char-acterized by a broken time-reversal symmetry (BTRS). Not only is it the simplest extension of the most abundant s-wave state that breaks time-reversal symmetry, but also it is expected to arise from various microscopic mechanisms. Recently it was demonstrated that such state very likely occurs in some iron based superconductors. [1]. Although the underlying microscopic physics is not exotic, nor is any fine tuning is required to form such a state, no experimental observations of such BTRS states have been reported. The reason being the major challenges to distinguish the s+is state from its time-reversal invariant s+- and s++ cousins. Indeed, the probe of relative phases between components of the order parameter in different bands is a non-trivial task [2].

We discuss possible direct manifestations of BTRS state in experimentally observable transport and magnetic properties of s+is superconductors. At first we show that the existence of mixed phase-density modes in multiband superconductors with broken time-reversal symmetry generates a new contribution to the viscosity of magnetic flux flow [3]. Near the time reversal symmetry breaking phase transition this new contribution dominates over the usual Tinkham and Bardeen-Stephen [4] mechanisms and provides a peculiar temperature dependence of the vortex viscosity. Second, we point out the unusual thermoelectric properties of BTRS superconductor. Namely we predict a generic contribution to the thermally induced supercurrent, whose direction is not invariant under time reversal operation [5]. Besides, that contribution can be orders of magnitude larger than the ordinary one and, in contrast to Ginzburg's mechanism [6], be present even at low temperatures.

1. S. Maiti, A. V. Chubukov, Phys. Rev. B 87, 144511 (2013); F. Ahn, I. Eremin, J. Knolle, V. B.

Zabolotnyy, S. V. Borisenko, B. Büchner, and A. V. Chubukov, Phys. Rev. B 89, 144513 (2014). 2. M. Marciani, L. Fanfarillo, C. Castellani, and L. Benfatto, Phys. Rev. B 88, 214508 (2013). 3. M. Silaev, E. Babaev, Phys. Rev. B 88, 220504 (2013) 4. M. Tinkham, Introduction to superconductivity, Dover Publications (2004). 5. M. Silaev, J. Garaud, E. Babaev, arXiv:1503.02024 6. V. L. Ginzburg, Zhurnal Eksperimentalnoi i Teoreticheskoi Fiziki 14, 177 (1944).

FRIDAY



The introduction of subthreshold induced defects in germanium by above threshold radiation exposure

S.M.M. Coelho1,*, J.F.R. Archilla2 and F.D. Auret1 1Department of Physics, University of Pretoria, Lynnwood Road, Pretoria 0002, South Africa

2Group of Nonlinear Physics, Universidad de Sevilla, ETSII, Avda Reina Mercedes s/n, 41012-Sevilla, Spain

* [email protected]

Ultrapure germanium doped with antimony to a concentration of 1015 cm-3 was irradiated

with α-particles from an americium-241 source. The defects introduced have been reported on before and remain, except for the e-center, unidentified [1]. By subjecting a second sample to a low energy (20 eV) Ar plasma etch and subsequent anneal the number of defects that were previously undetectable by deep level transient spectroscopy (DLTS) were further reduced. Such plasma etched germanium has been shown to be impervious to defect introduction in processes like electron beam deposition that typically exposes materials to subthreshold irradiation. Comparing the defects introduced when the second sample was exposed to α-particle irradiation by the same source yielded the following results. While the e-center introduction remained largely unchanged, the concentration of all other defects was lowered to some degree. E0.21 and E0.24 that are typically observed after α-particle irradiation were absent from the DLTS spectrum of sample 2. These differences in the spectra indicate that in the control, more than one defect creation process was responsible for the defects observed whereas in sample two only the defects that are created by the displacement of native germanium atoms were observed.

1. F. D. Auret, W. E. Meyer, S. Coelho, M. Hayes, “Electrical characterization of defects

introduced during electron beam deposition of Pd Schottky contacts on n-type Ge.” Applied Physics Letters, 88(24), 242110 (2006).

FRIDAY



The dynamics of dimers and dipoles on a surface

E. Heinsalu1,*, M. Patriarca1, F. Marchesoni2 1 National Institute of Chemical Physics and Biophysics, Rävala 10, 15042 Tallinn, Estonia

2 Dipartimento di Fisica, Università di Camerino, I-62032 Camerino, Italy * [email protected]

One particular example of Brownian motion on a periodic substrate is the diffusion of

atoms and molecules on crystal surfaces. This mechanism is of both conceptual and technological interest. Individual atoms diffusing on a surface can eventually meet and form dimers or trimers. For example, on a semiconductor Si(100) or Ge(100) surface, most of the deposited Si or Ge atoms form dimers. This raises the issue of the role of the internal degrees of freedom on the transport of extended objects through micro- and submicrondevices.

In this presentation, the transport of a dimer, consisting of two Brownian particles bounded by a harmonic potential, moving on a symmetric periodic substrate under the influence of a dc field is discussed, with focus on the effects of the internal degrees of freedom on its mobility and diffusivity [1, 2]. For simplicity, the analysis is restricted to substrates in two or higher dimensions that can be reduced to one-dimensional (1D) systems. The mobility and diffusion of the center of mass present distinct properties when compared with those of a monomer under the same transport conditions. The influence of dimer equilibrium length, coupling strength, and damping constant on the dimer transport properties are also examined.

Contrary to the case of a dimer, in the case of a neutral dipole, made up of two bound equal pointlike masses carrying opposite charges, an external electric field pulls the monomers to opposite directions. The field, no matter whether dc or ac, cannot induce a net dipole current, since the total force applied to the dipole center of mass is zero. As a consequence, the motion of the center of mass on a symmetric substrate is purely diffusive. However, the internal degree of freedom of a dipole, when constrained to 1D and subjected to an oscillating field of force, exhibits interesting properties [3]. It is observed that the amplitude of the forced oscillations of the dipole can be enhanced by tuning the noise strength, i.e., the substrate temperature. Such a manifestation of stochastic resonance turns out to be sensitive to the mechanical properties of the dipole [3, 4], having immediate applications to surface physics and nanotechnology.

1. E. Heinsalu, M. Patriarca, F. Marchesoni, "Dimer diffusion in a washboard potential", Physical

Review E 77, 021129 (2008). 2. M. Patriarca, E. Heinsalu, P. Szelestey, "Brownian model of dissociated dislocations", Acta

Physica Polonica B 36, 1745 (2005). 3. E. Heinsalu, M. Patriarca, F. Marchesoni, "Stochastic resonance in a surface dipole", Chemical

Physics 375, 410 (2010). 4. E. Heinsalu, M. Patriarca, F. Marchesoni, "Stochastic resonance in bistable confining potentials",

European Physical Journal B 69, 19 (2009).

FRIDAY



Ab initio simulations of discrete breathers in graphane and deformed graphene

G.M. Chechin*, S.V. Dmitriev, G.S. Bezuglova, I.P. Lobzenko, D.S. Ryabov

Southern Federal University, Institute of Physics, Stachki Ave., 194, 344090, Rostov on Don, Russia [email protected]

Graphane (fully hydrogenated graphene) can be considered as a system that consists of

graphene sheet with hydrogen atoms attached to it at the opposite sides of the sheet in a staggered manner. Discrete breathers (DBs) represent localized in space and periodic in time oscillations in homogeneous nonlinear Hamiltonian lattices. DBs were found experimentally in some mesoscopic systems, but it is very difficult to observe them in crystals. In this regard, an important role in studying DB properties play methods of mathematical modelling. Almost all computer simulations of discrete breathers rely on the mass-points models with interactions described by some phenomenological potentials. However, such models are not rather adequate since they do not take into account the effects of the atoms’ electron shell polarization. Moreover, such effects require the quantum mechanical description.

First ab initio studying of discrete breathers in graphane was carried out in our paper [1] by the methods of density functional theory [2] with the aid of ABINIT software package. The Born-Oppenheimer approximation was applied to separate the fast movement of electrons and slow movements of atom nuclei. The behavior of electron subsystem was described by quantum-mechanical Kohn-Sham equations, while atom cores were considered as classical particles. The exchange-correlation functionals were taken in the standard local density approximation (LDA) form. We found a number of significant differences in the properties of the obtained discrete breathers compared to those published in [3], which were investigated in the model of mass points, interacting via phenomenological potential.

In this work, we consider the refining of DB shape in graphane with the aid of some optimization procedure and study the time-evolution of the system dipole moment in the process of breather vibrations. We also study DB in graphene whose frequency lies in the pho-non-spectrum gap induced by uniaxial strain in zigzag or armchair directions. Special attention is paid to study the frequency-amplitude dependence of the in-plane gap breathers, as well as to investigate deviation from strict time periodicity of the breather-like dynamical objects (quasibreathers [4]) arising from the relative displacements of two neighboring graphene atoms.

1. G. M. Chechin, S. V. Dmitriev, I. P. Lobzenko, D. S. Ryabov. Phys. Rev. B 90, 045432 (2014). 2. W. Kohn. Rev. Mod. Phys. 71, 1253 (1999). 3. J. A. Baimova, S.V. Dmitriev and K. Zhou. Europhys. Lett. 100, 36005 (2012). 4. G. M. Chechin, G.S. Dzhelauhova and E.A. Mehanoshina. Phys. Rev. E 74, 036608 (2006).

FRIDAY



Self-organized surface structures produced by ultrafast white-light supercontinuum

S. Uhlig1,2,*, O. Varlamova1, J. Reif1, M. Ratzke1 1Brandenburgische Technische Universitaet – BTU Cottbus-Senftenberg,

Platz der Deutschen Einheit 1, 03046 Cottbus, Germany 2present address: Fraunhofer IPMS, Maria-Reiche Str., Dresden, Germany

* [email protected]

The sub-micron modification of solid surfaces by femtosecond-laser induced periodic surface structuring (LIPSS) has found increased attraction in recent years [1], in particular because of a wide field of possible applications such as wettability modification [2], friction reduction [3], biological templates or scaffolds [4],[5], color [6] or reflectivity change [7], or templates for surface enhanced processes [8]. Nevertheless, the underlying physical mechanism is not yet unambiguously clear. There are, mainly, two scenarios under discussion: (1) a lithographic process [9],[10], involving a laser generated periodic (interference) pattern; (2) our model of a dynamic process based on a laser-induced surface instability relaxing by self-organized structure fomation [11],[12]. In scenario (1), the laser, in particular its wavelength and coherence, plays the dominant role for structure formation. In scenario (2), only the deposited energy and an active reaction of the target material are responsible for the structures, whereas the laser wavelength is not involved. Here, we present the formation of LIPSS using a non-coherent white light continuum between 400 nm and 700 nm. On different types of targets Si(100); copper, brass, stainless steel we find the same type of regular nanostructures as with coherent laser irradiation. Even the feature sizes ("ripples wavelengths") are very close to those produced by coherent 800-nm laser pulses. The experimental results show that coherent laser light at a well-defined wavelength is not essential for light-induced periodic surface structuring. Thus, they strongly confirm our scenario (2) and, in a way, somewhat debase scenario (1).

1. Vorobyev, A.Y., Guo, C., Laser & Photonics Review 7, 385 (2013) 2. Wu, B., Zhou, M., Li, J., Ye, X., Li, G., Cai, L., Appl. Surf. Sci. 256(1), 61-66 (2009). 3. Tagawa, N., Takada, M., Mori, A., Sawada, H., Kawahara, K., Tribol. Lett. 24(2), 143-149

(2006). 4. Wang, X., Ohlin, C. A., Lu, Q., Hu, J., Biomaterials 29(13), 2049-2059 (2008). 5. Yang, Y., Yang, J., Liang, C., Wang, H., Zhu, X., Zhang, N., Opt. Express 17(23), 21124-21133

(2009) 6. Dusser, B., Sagan, Z., Soder, H., Faure, N., Colombier, J. P., Jourlin, M., Audouard, E., Opt.

Express 18(3), 2913-2924 (2010) 7. Vorobyev, A. Y., Makin, V. S., Guo, C., Phys. Rev. Lett. 102(23), 234301 (2009) 8. Diebold, E. D., Mack, N. H., Doorn, S. K., Mazur, E., Langmuir 25(3), 1790-1794 (2009) 9. Sipe, J.E., Young, S.F., Preston, S.S., van Driel, H.M, Phys. Rev. B 27, 1141(1983) 10. Bonse, J., Rosenfeld, A., Krüger, J., J. Appl. Phys. 106, 104910 (2009) 11. Varlamova, O., Reif, J., Varlamov, S., Bestehorn, M., J. Nanosci. Nanotechnol. 11, 9274 (2011) 12. Reif, J., Varlamova, O., Varlamov, S., Bestehorn, M., Appl. Phys. A. 104, 969 (2011).

FRIDAY



Methods of statistical topography for revealing anomalous long-range correlations in disordered media

J. Kalda*, I. Mandre

Institute of Cybernetics, Tallinn University of Technology, Akadeemia tee 21, 12618, Tallinn, Estonia [email protected]

Most typically, long-range correlations in disordered media manifest in the form of power

laws. Statistical topography provides a series of tools and methods for studying such correlations. On the basis of a random field with long-range correlations, random surface(s) can be built. For instance, in the case of admixture concentration field ( , )c x y , we define the

surface in ( , , )x y z - space as ( , )z c x y . Depending on the value of the correlation power law

exponent, either the surface ( , )z c x y itself, or its higher order derivatives are statistically

self-affine, and can be described by the Hurst exponent H , defined via the scaling law

| ( ) (0) | ~| |Hc c r r ; here, ... denotes averaging over an ensemble of realizations. Apart

from the exponent H , there is a series of scaling exponents characterizing such surfaces, including various fractal dimensions (e.g. of the isolines). If the surface has Gaussian statistics, all these exponents are functions of the Hurst exponent H . Several examples of such scaling exponents will be discussed, and a brief overview of relevant numerical methods is given. Also, scaling laws related to the intersections of self-affine surfaces with lines and planes are discussed. So, in the case of Gaussian fields, a series of scaling exponents are known functions of the Hurst exponent H . Based on this finding, it is possible to judge the degree of non-Gaussianity of the fields: in the case of significant non-Gaussianity, the expected dependence between the scaling exponents and H will not be observed; a relevant example is provided.

SATURDAY



Doping dependent band structure and pairing in strongly correlated electron systems of high-Tc cuprates

S.G. Ovchinnikov1,2,*, E.I. Shneyder1, M.M. Korshunov 1,2, V.A. Gavrichkov1, I.A. Makarov1

1 Kirensky Institute of Physics, 50/38 Akademgorodok, Krasnoyarsk, 660036, Russia 2 Siberian Federal University, 89 Svobodnii Prospekt, Krasnoyarsk, 660041, Russia

* [email protected]

In the multielectron generalized tight-binding (GTB) approach and its ab initio version

LDA+GTB the electronic band structure of strongly correlated material depends on the occupation numbers of local (CuO6 unit cell) multielectron states. It results in strong concentration and temperature dependent band structure. For La2-xSrxCuO4 we have calculated self-consistently the doping dependence of electronic and spin–liquid correlation functions at low temperatures. Evolution of the hole Fermi surface with doping occurs throw two Lifshits-type quantum phase transitions. The first one at xc1=0.15 determines the optimal doping, and the second at xc2=0.24 separates at T=0 the pseudogap and the Fermi liquid states. A mean-field theory of d-wave superconductivity in regime of strong electron correlations with both magnetic and phonon pairing is developed. The only uncalculated ab initio parameter of the effective electron-phonon coupling G is obtained from fitting the isotope effect at optimal doping, the ration G to the exchange coupling J appears to be close to 1 With this value of elec-tron-phonon coupling both magnetic and phonon contributions to Tc are of the same order of magnitude[1]. In the bilayer cuprates the Lifshitz transitions are splitted by the interlayer coupling. The interlayer coupling and exchange interaction does not increase the superconducting critical temperature.

(*) This work is supported by the Russian scientific foundation, the grant 14-02-00061.

1. S.G.Ovchinnikov, V.A.Gavrichkov, M.M.Korshunov, E.I.Shneyder, LDA+GTB method for band structure calculations in the strongly correlated materials. In the “Theoretical Methods for strongly Correlated systems”, Ed. A.Avella, F.Mancini, Springer Series in Solid-State Sciences. Volume 171, 143-171, Springer-Verlag Berlin Heidelberg, 2012

SATURDAY



Elementary excitations in the symmetric spin-orbital model

M.Yu. Kagan1,2, K.I. Kugel3, A.V. Mikheyenkov4,5,*, A.F. Barabanov4 1 Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, 119334 Russia

2 National Research University Higher School of Economics, Moscow, 109028 Russia 3 Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, Moscow,

125412 Russia 4 Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow, 142092 Russia

5 Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow region, 141700 Russia

* [email protected]

Possible types of elementary excitations in the symmetric spin-orbital (Kugel-Khomskii)

model on a square lattice are considered. We base our treatment on the spherically symmetric self-consistent approach providing reliable results for low-dimensional spin systems [1]. The dependence of correlation functions involving both spin and orbital variables on temperature and parameters of the model is analyzed. The spectra of different elementary excitations characteristic of the model under study are calculated. It is shown that the thermodynamics of the system is mainly determined by elementary excitations with the entangled spin and orbital degrees of freedom [2]. We also demonstrate the formation of the state with nonzero values of the correlation functions corresponding to the entanglement of the spin and orbital degrees of freedom. The transition to such a state resembles by its characteristics a second-order phase transition. The corresponding schematic phase diagram is constructed.

1. A.F. Barabanov, A.V. Mikheyenkov, and A.V. Shvartsberg, "Frustrated quantum two-

dimensional J1-J2-J3 antiferromagnet in a spherically symmetric self-consistent approach", Theor. Math. Phys. 168, 1192 (2011).

2. M.Yu. Kagan, K.I. Kugel, A.V. Mikheyenkov, and A.F. Barabanov, "Elementary excitations in the symmetric spin-orbital model", JETP Lett. 100, 187 (2014).

SATURDAY



Electronic structure of the Hubbard and t-J models within the cluster perturbation theory in the X-operators representation

S.V. Nikolaev1,2,*, V.I. Kuz’min1, S.G. Ovchinnikov1,2 1 Kirensky Institute of Physics, 50/38 Akademgorodok, Krasnoyarsk, 660036, Russia 2 Siberian Federal University, 89 Svobodny Prospekt, Krasnoyarsk, 660041, Russia

* [email protected]

The discovery of high-Tc cuprates has resulted in intensive studies of the electronic

structure of doped Mott insulators. Experimental data have revealed a radical evolution of electronic structure upon doping. The most unusual state found in a wide doping range between a weakly doped insulator and overdoped Fermi liquid is the pseudogap state. The origin of the pseudogap state is still an unresolved problem. The two-dimensional (2D) Hubbard model is a relevant low-energy model for cuprates. The t-J model obtained by eliminating the excitations over the Mott-Hubbard gap U in the limit U>>t, where t is the nearest neighbor hopping parameter. It should be noted that the unitary transformation of the Hubbard model Hamiltonian results in the so-called t-J* model. The t-J* Hamiltonian has an additional three-site correlated hopping H3 above the t-J Hamiltonian. Quite often this term is neglected. Nevertheless, there are some indi-cations that the H3 term may be important in the formation of the superconducting state with d-wave symmetry.

We have compared the band dispersion and DOS in the normal phase of the Hubbard model and the t-J model within the CPT approach in X-operators representation [1] and find that the differences for these two models become negligibly small when taking into account the H3 term [2]. It means that the Hubbard model and the t-J* model provide indeed similar electronic structure, while the electronic structure of the t-J model at the high-energy scale ω >~ t differs remarkably from the one obtained within the Hubbard model. As concerns the low-energy scale ω <~ J, all three models give similar results. Our other finding is zeros of the Green function for the t-J and t-J* models that were obtained earlier for the Hubbard model. Our results are in qualitative agreement with CDMFT calculations.

(*) This work is supported by RFBR (Grants No. 13-02-01395-a, No. 14-02-31677-mol-a, and No. 14-02-00186-a), the Ministry of Education and Science of Russia (Government Contract No. 3085, SibFU 2014 GF-2), and a grant of the Russian President (Grant No. NSh-2886.2014.2).

1. S.V. Nikolaev and S.G. Ovchinnikov. "Effect of hole doping on the electronic structure and the

Fermi surface in the Hubbard model within norm-conserving cluster pertubation theory", JETP 114 (1), 118-131 (2012).

2. V.I. Kuz‘min, S.V. Nikolaev and S.G. Ovchinnikov. "Comparison of the electronic structure of the Hubbard and t-J models within the cluster perturbation theory", Phys.Rev.B 90 (24), 245104(5) (2014).

SATURDAY



Static and dynamical correlations of strongly disordered superconductors

G. Seibold1,*, L. Benfatto2, J. Lorenzana2 and C. Castellani2 1Institut für Physik, BTU Cottbus-Senftenberg, PBox 101344, 03013 Cottbus, Germany

2Dipartimento di Fisica, Università di Roma ``La Sapienza'', P. Aldo Moro 2, 00185 Roma, Italy * [email protected]

In the last decades the failure of the BCS paradigm of superconductivity in several

correlated materials led to a profound modification of the description of the superconducting phenomenon itself. A case in point is the occurrence of Cooper pairing and phase coherence at distinct temperatures, associated respectively with the appearance of a single-particle gap and a non-zero superfluid stiffness. This particular behavior is observed in several materials, which range from high-temperature cuprate superconductors to strongly-disordered films of conventional superconductors. For the latter systems scanning tunneling microscopy measurements have revealed that the superconducting state becomes inhomogeneous, segregating into domains of large and suppressed superconducting order parameter. In this contribution we will discuss the static and dynamical response of such systems based on studies of the attractive Hubbard model with strong on-site disorder and by including fluctuations beyond the Bogoljubov-de Gennes approach.

We find a decoupling of charge and amplitude correlations with increasing disorder due to the formation of superconducting islands. This emergent granularity also induces an enhancement of the charge correlations on the SC islands whereas amplitude fluctuations are most pronounced in the 'insulating' regions. While charge and amplitude correlations are short-ranged at strong disorder we show that current correlations have a long-range tail due to the formation of percolative current paths in agreement with the constant behavior expected from the analysis of the one-dimensional xy-model. Moreover we show that for strongly disordered superconductors phase modes acquire a dipole moment and appear as a subgap spectral feature in the optical conductivity.

SATURDAY



Nonlinear localized modes in biomolecular structure

F. Piazza*, Y.-H. Sanejouand

University of Orléans and Centre de Biophysique Moléculaire CNRS UPR4301, Rue Charles Sadron, 45071, Orléans, France

* [email protected]

Coarse-grained elastic-network models of proteins provide considerable insight in protein

functional dynamics at reduced computational cost. In particular, analysis of low-frequency, collective normal modes (NM) has emerged as a powerful tool in many contexts to describe con-formational rearrangements of macromolecules directly linked to their function.

However, somewhat surprisingly, it turns out that coarse-grained network schemes are able to unearth interesting information also from the high-frequency region of their vibrational spectra. In particular, a nonlinear version of the elastic network model has been proposed recently, where the ability of high-frequency NMs to spotlight specific, function-related hot-spot sites is magnified. In the presence of nonlinear interactions, specific space-localized vibrational modes of nonlinear origin emerge, known as Discrete Breathers (DB). These modes are robust to perturbations and localize preferentially at a handful of very specific sites in a given structure, typically in the stiffest regions. Moreover, DBs are able to harvest energy from the background, assisting targeted energy transfer across specific and seemingly fold-encoded transduction path-ways.

In this talk I will review recent research conducted on these topics [1-5], highlighting the potential implications of high-frequency NMs and DBs in shedding light on the structural and dynamical determinants of important biological phenomena, such as allosteric communication, exciton transfer in light-harvesting complexes and enzyme catalysis.

1. F. Piazza and Y.-H. Sanejouand, “Long-range energy transfer in proteins”, Physical Biology - 6 ,

046014 (2009). 2. F. Piazza and Y.-H. Sanejouand, „Energy transfer in nonlinear network models of proteins“,

Europhysics Letters - 88 , 68001 (2009). 3. S. Luccioli, A. Imparato, S. Lepri, F. Piazza and A. Torcini, “Discrete breathers in a realistic

coarse-grained model of proteins”, Physical Biology - 8, 046008 (2011). 4. F. Piazza, “Nonlinear excitations match correlated motions unveiled by NMR in proteins: a new

perspective on allosteric cross-talk”, Physical Biology - 11, 036003 (2014). 5. V. I. Dubinko and F. Piazza, “On the role of disorder in catalysis driven by discrete breathers”,

Letters on Materials - 4(4), 273-278 (2014).

SATURDAY



Get your conductivity the typical way

W. Brenig*, R. Steinigeweg

Institute for Theoretical Physics, Technical University of Braunschweig, 38106 Braunschweig, Germany

* [email protected]

We will provide insights which emerge from the new concept of quantum typical pure-

state propagation as applied to the real-time dynamics of spin- and energy currents in quasi one-dimensional spin chain and ladder systems at finite temperature. It will be shown, that typicality is satisfied over a substantial range of temperatures, is fulfilled both, in integrable and nonintegrable systems, and significantly improves existing results from exact diagonalization, Lanczos, and time-dependent density matrix renormalization group. For the integrable case, the long-time dynamics of the spin currents and the spin Drude weight will be extracted beyond previously accessible combinations of system sizes and time domains. Strong evidence will be provided for the high-temperature spin Drude weight to vanish at the isotropic point. For a nonintegrable case, the heat conductivity of a spin ladder will be discussed over the entire range from weak to strong rung coupling.

SATURDAY



Effect of discrete breathers on the rate of chemical and nuclear reactions in solids

V.I. Dubinko

NSC Kharkov Institute of Physics and Technology, Kharkov 61108, Ukraine [email protected]

Excitation of discrete breathers (DBs) in solids are argued to result in the amplification of

the reaction rates in their vicinity. Two cases considered include chemical and low energy nuclear reactions (LENR). In the former case, the amplification mechanism is based on modification of the classical Kramers escape rate from a potential well due to a periodic modulation of the well depth (or the reaction barrier height), which is an archetype model for chemical reactions since 1940 [1, 2]. In the LENR case, it is argued that coherency and persistence of large atomic oscillations in breathers may have drastic effect on quantum tunneling due to correlation effects discovered by Schrödinger [2] and Robertson [3] in 1930. These effects have been applied to the tunneling problem by Dodonov et al in 1980 [4] and by Vysotskii et al in 2010 [5, 6], who demonstrated a giant increase of sub-barrier transparency (by 40 to 100 orders of magnitude) during the increase of correlation coefficient at special high-frequency periodic action on quantum system. We argue that DBs is the most efficient way to produce such an action due to time-periodic modulation of the potential well width (or the Coulomb barrier width) and hence to act as breather nano-colliders (BNC) triggering LENR [7]. DBs have been shown to arise either via thermal activation at elevated temperatures (E-Cat type reactors) or via knocking atoms out of equilibrium positions under non-equilibrium gas loading conditions (electrolysis or plasma deposition methods). The DB statistics in both cases is analyzed, and the DB-induced LENR rate is shown to depend exponentially on temperature and linearly on the electric (or ion) current, in agreement with experiments. Possible ways of engineering the nuclear active environment based on the present concept are discussed [8, 9].

1. V.I. Dubinko., P.A. Selyshchev, J.F.R. Archilla, Phys. Rev. E 83 (2011) doi:

10.1103/PhysRevE.83.041124. 2. E. Schrodinger, Ber. Kgl. Akad. Wiss., Berlin, S. 296-303 (1930). 3. H.P. Robertson, Phys. Rev. 34, 163-164 (1930). 4. V.V. Dodonov, V.I. Man’ko, Phys. Lett. A 79 (2/3), 150-152 (1980). 5. V. I. Vysotskii, S. V. Adamenko, J. Tech. Phys. 55 (5), 613-621 (2010). 6. V. I. Vysotskii, M.V. Vysotskyy, Eur. Phys. J. A (2013) DOI 10.1140/epja/i2013-13099-2. 7. V.I. Dubinko, A.V. Dubinko, “Quantum Tunneling in Breather ‘Nano-colliders’”, ICCF-19,

2015. 8. V. I. Dubinko, J. Condensed Matter Nucl. Sci. 14, 87-107 (2014) 9. V. I. Dubinko, F. Piazza, Letters on Materials 4 (4), (2014)273-278

SATURDAY



Numerical experiments of dislocation nucleation

M. Patriarca1,*, A. Kuronen2, K. Kaski3 1National Institute of Chemical Physics & Biophysics, Rävala 10, Tallinn 15042, Estonia

2 Department of Physics, Accelerator Laboratory, P.O. Box 43, FIN-00014, Finland 3 Department of Biomedical Engineering and Computational Science,

P.O.Box 12200, FI-00076 Aalto,Finland * [email protected]

Misfit dislocations in heterostructures represent a topic of both technological and general

interest [1,2]. They arise from instabilities appearing during the growth of the overlayer of the heterostructure, due to kinematic or geometric factors of the molecular beam, if the the molecular beam epitaxy technique is used [3], or can have a thermodynamical origin. Here misfit dislocation originating from thermodynamical instabilities are studied, that are independent of the details of the preparation technique and only related to the properties of the two materials. We make numerical gedanken-experiments of systems initially composed by A and B type atoms different from each other only formally. The inter-atomic potential parameters of atoms A are then adiabatically varied towards the values of the overlayer atoms interatomic potential. Dislocations loops are observed to nucleate and enlarge until they reach the surface of the system leaving stacking faults. The conditions for nucleation are determined numerically and compared with theoretical continuum models [4]. Full molecular dynamics simulations are employed for describing the thermally activated nature of dislocation nucleation [5]. We use both a light molecular dynamics code for longer simulations and codes coupled to an interactive graphical user interface for a more effective visualization of the ongoing physical processes [6]. Visualization algorithms are based on the atomic potential energy or the atomic displacements. As a toy model, a simple Lennard-Jones potential and an EAM potential are used and compared with each other.

1. W.K. Liu, M.B. Santos, Eds., Thin films: Heteroepitaxial systems, vol. 15, Series on Directions

in Condensed Matter Physics (World Scientific, Singapore, 1999). 2. A. Kuronen, M. Patriarca, Atomistic modeling of hetero-structures, in: Handbook of Theoretical

and Computational Nanotechnology, M. Rieth, W. Schommers,Edts., Am. Sci. Pub. (2005). 3. P. Politi, G. Grenet, A. Marty, A. Ponchet, J. Villain, “Instabilities in crystal growth by atomic or

molecular beams”, Phys. Rep. 324 (2000) 271. 4. R. Hull and J. C. Bean, “Misfit dislocations in lattice-mismatched epitaxial films”, Crit. Rev. Sol.

State Mat. Sci. 17, 507 (1992). 5. A. Kuronen, K. Kaski, L. Perondi, J. Rintala, Atomistic modelling of interaction between

dislocations and misfit interface, Europhys. Lett. 55 (2001) 19. 6. J. Merimaa, L. F. Perondi, K. Kaski, Comp. Phys. Comm. 124 (1999) 60. M. Patriarca, A.

Kuronen, M. Robles, K. Kaski, Comp. Phys. Comm. 176 (2007) 38.

SATURDAY



Discrete breathers in metals and ordered alloys

S.V. Dmitriev 1,*, P.V. Zakharov 2, E.A. Korznikova 1 1 Institute for Metals Superplasticity Problems RAS, Khalturin St. 39, 450001 Ufa, Russia

2 Altai State Academy of Education after V.M. Shukshin, Korolenko St. 53, 659333 Biysk, Russia * [email protected]

After the work by Haas et al. [1] there has been growing interest in the study of discrete breathers (DB) in pure metals. Such DB have frequencies above the phonon band. In this contribution, molecular dynamics method is used to demonstrate the possibility of excitation of two types of discrete breathers in the Pt3Al intermetallic compound. DB of the first type (DB1) is characterized by a high degree of localization on one light atom (Al) and its frequency lies in the gap of the phonon spectrum and decreases with increasing amplitude. In contrast, the second type of DB (DB2) is localized on a several light atoms, its frequency is above the phonon spectrum and increases with increasing amplitude. DB1 is immobile, while DB2 can move along the crystal close-packed direction. We study the collisions of two DB2 moving toward each other with equal velocities and the collisions between standing DB1 and moving DB2. Two DB2 collide almost elastically losing only a small part of their energy. DB2 is reflected by the standing DB1, but in this case the amount of radiation is greater. The results indicate that DB2 can transfer energy through the crystal over considerable distances.

We also report on some properties of DB in pure metals with fcc, bcc, hcp lattices and in uranium that has a low-symmetry lattice.

1. M. Haas, V. Hizhnyakov, A. Shelkan, M. Klopov, A. J. Sievers, Phys. Rev. B 84, 144303 (2011).

SATURDAY



On the theory of exact interactions between vibrational modes in physical systems with discrete symmetry

S. Shcherbinin, G.M. Chechin*, D.S. Ryabov

Southern Federal University, Institute of Physics, Stachki Ave., 194, 344090, Rostov on Don, Russia * [email protected]

We consider nonlinear vibrations in Hamiltonian systems. Conventional normal modes

are exact solutions of dynamical equations in the harmonic approximation. Such modes cease to be exact if some anharmonic terms are taken into account. In this connection one can ask: “Are there exist some exact solutions of nonlinear dynamical equations beyond the harmonic approximation?”

In [1], the concept of bushes of vibrational nonlinear normal modes (NNMs) for dynamical systems with discrete symmetry was introduced. Every bush possesses a certain symmetry group which is a subgroup of the group of the system in equilibrium state. It represents an exact solu-tion to nonlinear dynamical equations. The energy of initial excitation of a given bush turns out to be trapped in this dynamical object until it loses stability. The specific group-theoretical methods for constructing bushes of NNMs was developed in [1,2]. Only a finite number of bushes of each dimension can exist in the physical system with a given symmetry. The construction of bushes can be done without any information about concrete type of interparticle interactions: one must know only the symmetry group and the geometrical structure of the considered system. Geometrical and dynamical properties of one-, two- and three-dimensional bushes in simple octahedral systems of mass points interacting via some phenomenological potentials were studied in [3].

In the present work, we give the answer to the question: "Can the concept of bushes of nonlinear normal modes and the methods of their studying be valid for nonlinear dynamics of real physical systems?" In this study, we use ab initio simulations based on the density functional theory (DFT) [4], which proved to be very effective and rather correct for studying molecules and crystals. With the aid of DFT, we have investigated highly localized time-periodic vibrations in graphane (fully hydrogenated graphene) in [5]. Here we apply DFT for validating the theory of the bushes of vibrational modes using as an example the molecule SF6. For this purpose, we use the ABINIT software package.

We have revealed that the properties of excitation transfer between modes with different symmetry are in complete agreement with the bush theory.

1. V.P. Sakhnenko, G.M. Chechin. Phys. Dokl. 38, 219 (1993). 2. G.M. Chechin, V.P. Sakhnenko. Physica D 117, 43 (1998). 3. G.M.Chechin, A.V. Gnezdilov, M.Yu. Zekhtser. Int.J.Non-Linear Mech. 38, 1451 (2003). 4. W. Kohn. Rev. Mod. Phys. 71, 1253 (1999). 5. G. M. Chechin, S. V. Dmitriev, I. P. Lobzenko, D. S. Ryabov. Phys. Rev. B 90, 045432 (2014).

SATURDAY



Phonon interference and energy transport in nonlinear lattices with resonance defects

Yu.A. Kosevich1,2,*, H. Han2, L.G. Potyomina3, A.N. Darinskii4, S. Volz2 1Semenov Institute of Chemical Physics, Russian Academy of Sciences,

4 Kosygin Street, Moscow 119991, Russia 2CNRS, UPR 288 Laboratoire d’Energétique Moléculaire et Macroscopique, Combustion (EM2C)

and Ecole Centrale Paris, Grande Voie des Vignes, 92295 Châtenay-Malabry, France 3Department of Physics and Technology, National Technical University “Kharkiv Polytechnic

Institute”,21 Frunze Street, Kharkiv 61002, Ukraine 4Institute of Crystallography, Russian Academy of Sciences,

59 Leninskii Avenue, Moscow 119333, Russia * [email protected]

We introduce and model a three-dimensional atomic-scale phononic metamaterials

producing two-path phonon interference antiresonances to control the heat flux spectrum. We show that a crystal plane partially filled with defect-atom arrays produces a total phonon reflection at the frequency prescribed by masses and interaction forces. Such patterned atomic planes can be considered as high-finesse atomic-scale interference phonon metamirrors [1]. We emphasize the predominant role of the second phonon path and destructive interference in the origin of the total reflection in comparison with the Fano-resonance concept. The random defect distribution in the plane and the anharmonicity of atom bonds do not deteriorate the interference antiresonance. The width of the interference antiresonance dip can provide a measure of the coherence length of the phonon wave packet. All our conclusions are confirmed both by analytical studies of the equivalent quasi-one-dimensional lattice models and by numerical molecular dynamics simulations of realistic lattices in three dimensions.

1. H. Han, L. G. Potyomina, A. A. Darinskii, S. Volz, Yu. A. Kosevich, "Phonon interference and

thermal conductance reduction in atomic-scale metamaterials", Phys. Rev. B 89(18), 180301 (2014).

SATURDAY



Mechanism of dielectric loss in glass ceramics for microwave electronics

M. Letz1, H. Braun2, M. Hovhannisyan1, M. Kluge1 1SCHOTT AG, Hattenberg Str. 10, 55122 Mainz, Germany

2Graduate School of Material Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany * [email protected]

Driven by the rapid increase of wireless data transfer which roughly doubles in volume

every year, there is a strong trend in GHz electronics towards compact designs and increased complexity. Glass ceramics with paraelectric crystalline phases provide an alternative class of materials as dielectrics for microwave electronics, which can enable highly accurate and complex designs of antenna and filter elements. A key for developing such glass ceramics is the understanding of the mechanism of dielectric loss in these highly complex solids. In the current work we investigate the phonon structure of a LaTiSi-glass ceramic and derive, supported by synchrotron ellipsometry in the THz range, that phonon-phonon scattering is the dominant mechanism for dielectric loss at relevant microwave frequencies.

SATURDAY



Nonlinearily doped cuprate superconductors

J. Röhler

Universität zu Köln, Fachgruppe Physik, 50937 Köln, Germany [email protected]

Overdoped superconducting cuprates crystallize only near thermodynamic equilibrium. Unlike robust optimum (nn=0.16), and special (nh=0.125) underdoped states their synthesis deserves sophisticated solid state chemistry. Some cuprate families do not form at all in the overdoped regime. Mostly this does not root in too little chemical dopants or too little available sites in the spacing-, and separating layers, but in integer oxygen stoichiometry, e.g. in YBa2Cu3O7. Here co-substitution of the cations may overcome the constraints from the Cu - O stereochemistry, and thus open experimental access to the entire superconducting "dome". But often only nominally, since not every species of dopants, and not every site in the parent structure provides acceptor states for holes in the CuO2 planes. Note that spectroscopically evidenced hole counts [1] from nominally overdoped crystals (x=0.2-0.3) turn out to saturate around nh=0.19±0.02.

We elucidate the case of Bi2Sr2-xLaxCuO6+y [2]. Holes from substitution of Sr2+ by La3+ are found to compete strongly with ordinary charge compensation, meeting metastable mixtures of optimally doped Bi2Sr2-x(La,Bi)xCuO6+y throughout the entire overdoped regime.

The special stability of the optimum at nn=0.16, and hole saturation in the overdoped regime is shown to be of predominant electronic origin, inherent the Aufbau principles of the many body state in the doped parent Mott insulator. Next to strong Cud-d Coulomb repulsion significant Op-p Coulomb repulsion in the corner sharing O2px,y "cages" governs the many body interactions, inhibiting formation of nn(1a) hole singlets. Instead holes in a nnnn(3a) "nematic" may form singlets via intermediate excitation of spin triplets and thus gain kinetic energy. These "nematics" are oxygen centered along the Cu-O bonds and modulate the hole density with wavevector Qx,y=1/3 and a d - form factor [3]. The "nematic" hole density mode may couple to the Cu-O half-breathing lattice mode with Qx,y~1/3. With increasing nh a ladder-like mesostructure grows, being most densely packed at nopt=1/6. Hole numbers beyond nopt however will enforce formation of nn(1a) hole singlets, and thus collapse the ladder-like mesostructure of nnnn(3a) hole singlets. Accomodation of more holes tends to be inhibited by phase separation. The model is shown to be in line with the Q=0 mesostructure of pseudogap excitations observed with FT-STM and its collapse around nh=0.19 [4].

1. M. Schneider et al., PRB 72, 014504 (2005); D.C. Peets et al., PRL 103, 087402 (2009). 2. J. Röhler, Physica C 479 , S39 (2010). 3. J. Röhler, J. Superconductivity 17, 159 (2004); idem, Int. J. Phys 19, 255 (2005). 4. Y. Kohsaka et al., Science 315, 1380 (2007), Fujita et al. PNAS, 1406297111 (2014).

SATURDAY



Time resolved Raman scattering and VUV spectoscopy to study correlated oxides

M. Rübhausen

University of Hamburg, Luruper Chaussee 149, 22607 Hamburg, Germany [email protected]

SATURDAY



Polaronic effects in the strongly-correlated systems with strong electron-phonon interaction

I.A. Makarov1, S.G. Ovchinnikov1, E.I. Shneyder1, P.A. Kozlov1 1 Kirensky Institute of Physics, 50/38 Akademgorodok, Krasnoyarsk, 660036, Russia

[email protected]

There are many experimental evidences of strong electron-phonon interaction (EPI) in

HTSC cuprates. In order to take into account both EPI and strong electronic correlations (SEC) in these compounds we develop polaronic GTB (generalized tight-binding) method. Method GTB consists of (1) exact diagonalization of single cluster for different number of carriers, (2) construction of quasiparticle excitations between local multiparticle eigenstates using algebra of Hubbard operators and then transition to multiband Hubbard model and (3) cluster perturbation theory to describe electronic structure in the crystal lattice. In the polaronic GTB EPI terms are included in the Hamiltonian and local basis states for different carrier number nh are the product of the hole and phonon wave functions. At nonzero EPI carriers in the cluster is surrounded by lattice deformation which is expressed in the form of phonon “cloud”. Therefore cluster eigenstates are polaronic states, its wave functions are superpositions of the products of the electron and phonon wave functions. Polaronic effect depends on nh in the cluster. Excitations between states with different nh are Franck-Condon type processes.

In this work we investigate structure of local polaronic states and electronic structure of Franck-Condon type excitations in the crystal lattice for undoped La2CuO4 in the frameworks of three-band p-d-model. EPI acts between carriers and local phonons of optical breathing mode. We consider two regimes of EPI: only diagonal EPI and equal diagonal and non-diagonal EPI. In the diagonal EPI regime EPI constant growth leads to monotonic increase in the depth of potential well for hole on copper orbital, filling of this orbital, displacements of oxygen atoms. Phonon “cloud” of ground state spreads and moves to higher multiphonon states. Excited cluster eigenstates have more complex structure with several maxima in the “cloud”. Upper Hubbard band (UHB) and lower Hubbard band (LHB) of the quasiparticles in the system with EPI is formed by subbands of 0-, 1-, 2- etc. phonon processes. EPI increasing results in magnitude of splitting between subbands grows and width of subbands becomes smaller. Accordingly effective mass of Franck-Condon type excitations near the top of valence band and near the bottom of conductivity band will monotonically grow. In the regime of equal diagonal and non-diagonal EPI these two mechanisms partially compensate each other at small EPI constant, the phonon “cloud” is small, characteristics of polaron almost don’t change with varying magnitude of EPI. At EPI constant 0.31-0.33 abrupt redistribution of the hole density in the nh=1,2 states accompanied by full reconstruction of phonon “cloud” takes place. Low-energy quasiparticle excitations acquire large effective mass, its spectral weight is strongly suppressed. Spectral function of polaron quasiparticles at certain k is formed by several peaks.

(*) This work is supported by the Russian scientific foundation, the grant 14-02-00061.

SATURDAY



Unconventional ferrimagnetism of francisites Cu3Bi(SeO3)2O2X (X = Cl, Br)

A.A. Tsirlin1,*, I. Rousochatzakis2, R. Zinke3, and J. Richter3 1National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

2Max Planck Institute for Physics of Complex Systems, Dresden, Germany 3Institute for Theoretical Physics, University of Magdeburg, Germany

* [email protected]

The majority of low-dimensional quantum magnets are antiferromagnetic, while instances

of low-dimensional ferro- or ferrimagnetism are rare. Here, we show how net magnetic moments can be formed in systems of this type, and how low-dimensional ferrimagnets with tunable remnant magnetization can be designed. We illustrate this mechanism by the microscopic analysis of Cu2+ compounds Cu3Bi(SeO3)2X (X = Cl, Br) that are isostructural to the natural mineral francisite [1].

Francisite and its structural siblings feature low-dimensional spin systems. This magnetic low-dimensionality stems from their layered crystal structure, where exchange interactions in the ab plane of CuO4 plaquette units are about 50 times stronger than interactions between the planes. Each plane features ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor couplings on a kagome lattice of corner-sharing triangles. The competition between ferro- and antiferromagnetic couplings must result in a non-collinear spin configuration, but the system has the freedom to choose between an infinite manifold of classically degenerate spiral structures that are antiferromagnetic (net moment equal to zero) and a canted ferrimagnetic state with the non-zero net moment. We demonstrate that this ferrimagnetic state wins because of the combined effect of quantum fluctuations and magnetic anisotropy of Dzyaloshinsky-Moriya type.

Our work is based on a quantitative microscopic analysis that entails the evaluation of the full spin Hamiltonian, including isotropic (Heisenberg) and anisotropic (Dzyaloshinsky-Moriya, g-tensor) terms, from ab initio density-functional (DFT) calculations. The resulting spin Hamiltonian is analyzed using a variety of analytical (classical minimization, spin-wave theory) and numerical (exact diagonalization, coupled-cluster method) techniques, and the results are compared with the experiment. We show that the magnetic frustration and anisotropy stabilize ferrimagnetic order in a system that would be antiferromagnetic otherwise.

(*) This work is supported by the ESF (Mobilitas grant MTT77) and by the Estonian Research Council under PUT733.

1. I. Rousochatzakis, R. Zinke, J. Richter, and A. A. Tsirlin,"Frustration and Dzyaloshinsky-Moriya

anisotropy in the kagome francisites Cu3Bi(SeO3)2O2X (X = Cl, Br)", Phys.Rev. B 91, 024416 (2015).

2.

SUNDAY



One-dimensional electrons and photons: effects of interaction with two-level systems

V.I. Yudson1,2 1Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow 142190, Russia

2Russian Quantum Center, Skolkovo, Moscow Region 143025, Russia [email protected]

Interaction effects in one-dimensional systems are strong due to the reduced phase space.

The absence of spatial spreading of propagating particles (electrons, photons, etc.) results in long-range coupling of embedded two-level systems (spin impurities, quantum dots, resonant two-level atoms (TLA), etc.). Two examples of corresponding physical effects discussed here are: i) formation and decay of metastable excited states of spatially separated TLAs coupled with a photon waveguide [1]; ii) localization of helical electrons at the edge of a 2D topological insulator with Kondo spin impurities [2]. The both effects are due to multiple reflections of electrons or photons propagating through the one-dimensional system.

1. E.S. Redchenko, V.I. Yudson, "Decay of metastable excited states of two qubits in a waveguide",

Phys. Rev. A 90, 063829 (2014). 2. B.L. Altshuler, I.L. Aleiner, V.I. Yudson, "Localization at the Edge of a 2D Topological

Insulator by Kondo Impurities with Random Anisotropies", Phys.Rev.Lett. 111, 086401 (2013).

SUNDAY



Local structure of spin Peierls compound TiPO4: 47/49Ti and 31P NMR study

I. Heinmaa*, A. Leitmäe, E. Joon, R. Stern

National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn, 12618, Estonia * [email protected]

TiPO4 structure is made of slightly corrugated TiO2 ribbon chains consisting of edge-

sharing TiO6 octahedra. The chains are well separated by PO4 tetrahedra and the Ti3+ cations form almost perfect one-dimensional spin ½ chains. Recently by magnetic susceptibility and MAS-NMR measurements it was shown [1] that TiPO4 has nonmagnetic singlet ground state with remarkably high Spin-Peierls (SP) transition temperature. The high temperature magnetic susceptibility of TiPO4 follows well that of a S=1/2 Heisenberg chain with very strong nearest-neighbor AF spin-exchange coupling constant of J=965K. On cooling, unlike standard SP compounds (e. g. CuGeO3), TiPO4 shows two successive phase transitions at 111K and 74K, with incommensurate (IC) SP phase between these two temperatures.

In this report we present the study of the local structure and dynamics in TiPO4 single crystal using 47/49Ti and 31P NMR spectra and spin-lattice relaxation measurements in the temperature range 40K to 300K. The single crystal study allowed to determine the principal values and orientation of the magnetic shift tensors for 31P and 47,49Ti nuclei. In addition, since 47,49Ti (the spin numbers S=5/2 and S=7/2, respectively) have quadrupolar moments, we found the principal axis values and orientations of the electric field gradient (efg) tensor in SP phase and at 295K. We found that in SP phase the structure contains 2 magnetically inequivalent phosphorus sites, confirming the findings in [1] and only one titanium site. Comparison of the orientations of the principal axes of the efg tensor at titanium site in SP phase to that at high temperature showed that the charge distribution around titanium ions is almost the same at high and low temperatures in accord with recent synchrotron diffraction study [2]. From the temperature dependence of the relaxation rate of 31P and 47Ti nuclei we found an activation energy Ea = 550 K for spin excitations in SP phase.

1. J. M. Law, C. Hoch, R. Glaum, I. Heinmaa, R. Stern, J. Kang, C. Lee, M.-H. Whangbo, R. K.

Kremer, Phys. Rev. B 83, 180414 (2011). 2. M. Bykov, J, Zhang, A. Schönleber, A. Wölfel, S. I. Ali, S. van Smaalen, R. Glaum, H. J. Koo,

M. H. Whangbo, P. G. Reuvenkamp, J. M. Law, R. K. Kremer, Phys. Rev. B 88, 184420 (2013).

SUNDAY



Superconductivity in a multi-orbital Hubbard model

G. Litak1,*, T. Örd2, K. Rägo2, A. Vargunin2 1Lublin University of Technology, Nadbystrzycka 36, PL-20-618 Lublin

2Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia * [email protected]

We examine the properties of a superconductor described by a two-orbital negative-U

Hubbard model [1]. The superconducting phase transition is caused here by the on-site intra-orbital attractions and interorbital pair-transfer interaction. We find various characteristic lengths of the two orbital superconductors including the critical and noncritical coherence lengths, corresponding sizes of Coper pairs, and magnetic field penetration depth for different sets of system parameters. Numerical results have been obtained for a two-dimensional square lattice. The role of the interorbital proximity effect is also discussed.

1. G. Litak, T. Örd, K. Rägo, A. Vargunin, "Orbital effects on characteristic lengths in a two-orbital

superconductor", Physica Status Solidi B 251, 697-701 (2014).

SUNDAY



Competition between d-wave superconductivity and charge density waves: energy gaps and tunneling

A.M. Gabovich1,*, M.S. Li2, H. Szymczak2, A.I. Voitenko1 1Institute of Physics, National Academy of Sciences of Ukraine, 46, Nauka Ave.,Kyiv 03680, Ukraine

2Institute of Physics, Polish Academy of Sciences, 32/46, Al. Lotników,PL-02-668 Warsaw, Poland * [email protected]

A competitive coexistence of d-wave superconductivity and charge-density waves (CDWs) has been considered in the framework of the two-dimensional model appropriate to cuprates. The Fermi surface was supposed to be only partially gapped by CDWs. Both unidirectional and checkerboard CDWs were examined. The specific superconducting and CDW order parameters were determined from a system of coupled integral equations obtained in the mean-field approximation. It turned out that, for certain combinations of system parameters, the dielectric (CDW-related) order parameter can exist only in a restricted temperature, T, interval not including the point T = 0.

The Josephson current, I, in the ab crystal plane was calculated between two identical d-wave CDW superconductors or between a d-wave CDW superconductor and a conventional s-wave one. It was shown that the temperature, orientation, and certain other dependences of I are so modified by CDWs that the dielectric electron-hole pairing can be identified by measuring the coherent current.

The quasiparticle tunnel current, J, in the c-direction between two identical d-wave CDW superconductors or between a d-wave CDW superconductor and a normal metal was calculated. The voltage, V, dependences of the tunnel conductance, G, were shown to include a lot of peculiarities reflecting the intertwining of the superconducting and CDW order parameters and a complicated character of the combined gap profile that arises on the Fermi surface. Our theoretically predicted current-voltage characteristics are in agreement with the experimental results obtained for the stacks of Bi2Sr2CaCu2O8+δ symmetric tunnel junctions [1].

Calculations with the scattered values of the system parameters demonstrate that the intrinsic inhomogeneity observed in high-Tc oxides partially smooth off the G(V) peculiarities.

1. Ya. G. Ponomarev et al., "Quasiparticle tunneling in the c-direction in stacks of Bi2Sr2CaCu2O8+δ

S–I–S junctions and the symmetry of the superconducting order parameter ", Solid State Communs. 111 (9), 513-518 (1999).

SUNDAY



Magnetic field induced directional dichroism of THz light

T. Rõõm

National Institute of Chemical Physics and Biophysics, Tallinn, Estonia [email protected]

Multiferroics where magnetic and charge order are coupled have potential applications in

new type of memories, field sensors and spintronic devices. A large directional dichroism of THz light discovered recently in melilites [1-2] opens up the possibility to build unidirectional light switches. The directional dichroism is the property of material to have different absorption coefficient for counterpropagating light beams. In multiferroic materials the collective magnetic excitations, spin waves, are coupled to oscillations of electric dipoles similarly to dc magnetoelectric effect where the coupling is between static magnetization M and electric polarization P [3]. Because of optical (ac) magnetoelectric coupling the spin wave acquires electric dipole activity and interacts not only with the magnetic component but as well with the electric component of THz radiation. The symmetry of the material [4] and simultaneous magnetic and electric dipole activity of spin excitations are the key ingredients of the directional dichroism effect [5].

Magnetic field has played an important role in our THz spectroscopy studies of melilite-type multiferroics Ba2CoGe2O7, Sr2CoSi2O7 and Ca2CoSi2O7. Firstly, the magnetic field depend-ence of the THz absorption spectrum helped us to understand the nature of unusual spin stretching modes of electric dipole activity [6]. Secondly, the directional dichroism is activated by magnetic field and its sign and amplitude are field controlled. Thirdly, magnetic field gives rise to magnetochiral effect. Fourth, the directional dichroism is revived by application of high magnetic field even at elevated temperatures where the long range magnetic order is absent.

(*) This contribution has been made possible by the effort of authors of papers [1-6].

1. I.Kézsmárki, N. Kida, H. Murakawa, S. Bordács, Y. Onose, and Y. Tokura. Phys. Rev. Lett. 106, 057403, (2011).

2. S.Bordács, I. Kézsmárki, D. Szaller, L. Demkó, N. Kida, H. Murakawa, Y. Onose, R. Shimano, T. Rõõm, U. Nagel, S. Miyahara, N. Furukawa, Y. Tokura, Nature Physics 8, 734 (2012).

3. D.Szaller, S. Bordács, V. Kocsis, U. Nagel, T. Rõõm, I. Kézsmárki, Phys. Rev. B 89, 184419 (2014)

4. D.Szaller, S. Bordács, I. Kézsmárki, Phys. Rev. B 87, 014421 (2013) 5. I.Kézsmárki D. Szaller, S. Bordács, V. Kocsis, Y. Tokunaga, Y. Taguchi, H. Murakawa, Y.

Tokura, H. Engelkamp, T. Rõõm, U. Nagel, doi: 10.1038/ncomms4203, (2014). 6. K.Penc, J. Romhányi, T. Rõõm, U. Nagel, Á. Antal, T. Fehér, A. Jánossy, H. Engelkamp, H.

Murakawa, Y. Tokura, D. Szaller, S. Bordács, I. Kézsmárki, Phys. Rev. Lett. 108, 257203 (2012).

SUNDAY



Magnetic field induced ordering in clean and bond disordered quantum magnet DTN: neutron scattering and THz optical study

D. Hüvonen1,2,*, U. Nagel1, T. Rõõm1, E. Wulf2, K.Yu. Povarov2, A. Zheludev2 1 National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia

2 Neutron Scattering and Magnetism, Laboratory for Solid State Physics, ETH Zürich, Zürich, Switzerland

* [email protected]

Over the past decade, a great deal of attention has been devoted to so-called Bose-Einstein condensation of magnons observable in gapped quantum magnets. One of such prototype compounds, DTN, has gained renewed attention in the context of BEC in the presence of disorder. In experiments on Ni(Cl1-xBrx)2·4SC(NH2)2 (DTNX), where randomness is introduced on the non-magnetic halogen sites disorder was shown to substantially affect the (H-T) phase diagram. According to Yu et al.[1] the crossover exponent changes drastically to φ = 1 in the low-temperature regime T=250 mK. This behavior was interpreted in the context of Bose Glass physics though there remains a controversy regarding the value of φ even on the theoretical side. Confusingly, recent neutron diffraction experiments have measured the order parameter exponent β as well at the crossover exponent φ in DTNX [2], but failed to find any indication of Bose Glass behavior. I will review the efforts on extraction of the critical behavior near the quantum phase transition and show that the previous interpretations are severely affected by a distribution of transition fields in the sample [3]. I will discuss recent inelastic neutron scattering data for clean and disordered samples and the evolution of THz absorption spectrum through the ordered phase at temperatures below 1K and in magnetic fields up to 12T.

1. R. Yu et al., Bose glass and Mott glass of quasiparticles in a doped quantum magnet, Nature 489,

379 (2012) 2. E. Wulf et al., Criticality in a disordered quantum antiferromagnet studied by neutron diffraction.

Physical Review B 88, 174418 (2013) 3. E. Wulf et al., Critical exponents and intrinsic broadening of the field-induced transition in

NiCl2·4SC(NH2)2, Phys. Rev. B 91, 014406 (2015)

SUNDAY



On the method of evaluation of characteristics of quantum packets in the Jaynes-Cummings model

E.A. Karatsuba

Dorodnicyn Computing Center of RAS, Vavilov str. 40, Moscow, Russia 119333 [email protected]

A new approach to the study of the function of atomic inversion in the model of interaction of a single two-level atom with a single mode of the quantized electromagnetic field in the coherent state in an ideal resonator is discussed. It is based on an application of certain tools from number theory to approximate the trigonometric sums of a special form. New asymptotic formulas for the atomic inversion are found. These formulas allow us to predetermine the details of the behavior of the inversion on various time intervals depending on the parameters of the system.

1. E. T. Jaynes and F. W. Cummings,''Comparison of Quantum Semiclassical Radiation Theory

with Application to the Beam Maser", Proc. IEEE,51, 89–109 (1963). 2. N. B. Narozhny, J. J. Sanchez-Mondragon, and J. H. Eberly,''Coherence versus incoherence:

Collapse and revival in a simple quantum model'', Phys. Rev. A, 23, 236—247(1981). 3. E. A. Karatsuba, ''On an approach to the study of the Jaynes-Cummings sum in quantum optics'',

J. of Numerical Algorithms, 45(1-4), 127-137 (2007). 4. A. A. Karatsuba, E. A. Karatsuba, ''Application of ATS in a quantum-optical model''. Analysis

and Mathematical Physics: Trends in Mathematica Physics, Birkhauser Verlag, Basle, 209—230 (2009).

5. A. A. Karatsuba, E. A. Karatsuba, ''A resummation formula for collapse and revival in the Jaynes-Cummings model'', J. Phys. A: Math. Theor., 42, 195304, 1-16 (2009).

6. A. A. Karatsuba and E. A. Karatsuba, ''On Application of the Functional Equation of the Jacobi Theta Function to Approximation of Atomic Inversion in the Jaynes-Cummings Model'', Pacific Journal of Applied Mathematics, 2 (3), 41—63 (2010).

SUNDAY



Rotations and vibrations of water molecule inside the fullerene cage: infrared study of H2O@C60

A. Shugai1,*, T. Rõõm1, U. Nagel1, S. Mamone2, M. Concistrè2, S.B. Meier2, A. Krachmalnicoff2, J. Whitby2, M.H. Levitt2,

X. Lei3, Y. Li3, N.J. Turro3, Y. Murata4, T. Nishida4

1 National Institute of Chemical Physics and Biophysics, Akadeemia tee23, Tallinn, Estonia, 12618 2Chemistry, Uni. of Southampton, UK

3Dep. of Chemistry, Columbia Uni., New York 4Institute for Chemical Research, Kyoto University, Japan

* [email protected]

Water is the second molecule after hydrogen what has been trapped inside the cage of a

C60 molecule by the molecular surgery method [1]. The water molecule rotation transitions were observed in the THz [2] and vibration-rotation transitions in the mid-IR range. The slow conversion between para (two proton spins couple to form a singlet, I=0) and ortho (triplet, I=1) water allowed us to record the time evolution of spectra and to separate ortho and para absorption lines of water. The exact mechanism of the ortho to para conversion is still not fully understood, and we studied the relaxation process at different temperatures and concentration of H2O@C60 in order to clarify the kinetics. The similarity of the rotation spectrum of caged water to water in the gas phase indicates that water is free to rotate in the C60 cage even at temperature as low as 3K. However, spectral lines show a splitting of about 0.5 meV what is not compatible with the icosahedral symmetry of C60. Different models (e.g. crystal field effects in solid C60, C60 cage distortions) will be discussed.

1. K. Kurotobi, Y. Murata, “A Single Molecule of Water Encapsulated in Fullerene C60”, Science,

333 (6042), 613-616 (2011). 2. Beduz et al., “Quantum rotation of ortho and para-water encapsulated in a fullerene cage”, PNAS

109 (32), 12894 (2012).

Posters: Abstracts

POSTERS


53 P01 Posters: Abstracts

Covalence, electron localization and lattice dynamics controlled by polarization effects in the narrow-gap system FeAs2

A. Pishtshev1, P. Rubin1, M. Klopov2 1Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia

2Department of Physics, Faculty of Science, Tallinn University of Technology, Ehitajate 5, 19086 Tallinn, Estonia

*[email protected]

An integrated analysis of various charge, electronic and vibrational properties has shown

that lollingite FeAs2 is unique narrow-gap system in which polar As-Fe connections are playing a principal role in keeping the material away from the antiferromagnetic ground state. Combined DFT, DFT+U, and G0W0 calculations have revealed that such remoteness is a consequence of strong suppression of Coulomb repulsive interactions between 3d valence electrons at the iron sites. The main factor that governs the degree of delocalization of the 3d electron clouds is the strong interplay of electronic and polarization degrees of freedom. Of the significant interest was investigation of electronic channels that might cause the diamagnetic and insulating nature of the ground state of FeAs2. In particular, it was shown that genesis of the forbidden gap is entirely connected with an electronic ordering effect, which is determined by specific interrelation of structural and orbital degrees of freedom.

(*) The work was supported by the European Union through the European Regional Development Fund (Centre of Excellence "Mesosystems: Theory and Applications", TK114) and by the Estonian Science Foundation (grant No 8991).

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POSTERS



About mobile self-localized vibrations (ILM) in crystal lattices

M. Haas*, A. Shelkan

Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia [email protected]

At computer simulations of lattice excitations, the breather-type self-localized vibrational packets, moving along [110] or [111] atomic chains (mobile ILMs) has been created in metals Ni, Nb, Fe and Cu. In such chains, the vibrations of the neighboring atoms are characterized by phase shifts ( 2 , 0 corresponds to a standing ILM). Both the vibrational

frequency and the velocity of ILM 0 0v r t ( 0r is the interatomic distance in the chain)

depend on the vibrational amplitude and the aforementioned phase shift, the frequency exceeding the phonon spectrum. The slowly varying vibrational amplitude at a lattice site n

can be approximated as 0 0(t) cosh (t t ) ,n nA A . An analytical theory has been

developed, which describes the moving ILMs in an atomic chain located in a static lattice host and determines the dependencies of the characteristics , andv on the vibrational

amplitude 0A and the phase shift .

POSTERS


56 Posters: Abstracts P04

Bound states of benzene, graphene, carbon nanotubes and fullerenes: distortions, induced by pseudo-Jahn-Teller effect

V. Krasnenko, V. Boltrushko*

Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia * [email protected]

The structural element C6 consists of hexagonal carbon “ring” formed by sp2 hybrid

orbitals. It is the basic for many aromatic molecules and for new compounds, including fullerenes, carbon nanotubes and graphene. Recently it was found [1-3] that these rings may form conjoined structures, which may be important for their applications in nanoelectronics, optics, medicine, etc.

Here we present the results of analytical and density functional based numerical calculations of conjoined structures of two benzene molecules, benzene molecule with graphene sheets as well as chemically bound states of graphene sheets and carbon nanotubes. According to our calculations, the fullerenes can also form chemically bounded states. We have found such bound states formed by up to six (excluding three) bonds. In all these cases the chemical bonds between the structures are established by replacing the intra π-bonds of C6 rings by the inter σ-bonds. Irregular distortions of different π- bonds lead to the distortions in C6 rings.

We demonstrate that the reason of the distortion of C6 rings is the pseudo-Jahn-Teller effect (PJTE). In the simplest relevant case of two chemically bound benzene molecules (bi-benzene), three different distorted states in addition to one undistorted are found to exist [4]. PJTE leads also to a chemical bonding of three and more benzene molecules stacked directly on-top of each other. These bound structures do not exist for undistorted molecules. All bound states, although being metastable, are separated from the unbound ones by energy barriers (~2eV for bi-benzene). It is found that the height of the barrier for symmetric bi-benzene is essentially affected by the Jahn-Teller effect. The PJTE is also responsible for the formation of chemically bound states of benzene, graphene, carbon nanotubes and fullerenes.

Distorted benzene molecules can staple two benzene sheets, whilst undistorted can only form chemically bound state with a single graphene sheet. The discussed bound states, or at least some of them, presumably, may be obtained by means of UV excitation.

1. P. de Andres, R. Ramírez and J. Vergés, "Strong covalent bonding between two graphene layers"

Phys. Rev. B, vol. 77, pp. 045403-1 - 045403-5, 2008 2. V. Krasnenko, J. Kikas and M. Brik, "Modification of the structural and electronic properties of

graphene by the benzene molecule adsorption," Physica B, vol. 407, pp. 4557-4561, 2012. 3. V. Krasnenko, V. Boltrushko, M. Klopov and V. Hizhnyakov, "Conjoined structures of carbon

nanotubes and graphene ribbons," Physica Scripta, vol. 89, p. 044008, 2014. 4. V. Krasnenko, V. Boltrushko and V. Hizhnyakov, "Pseudo Jahn-Teller effect in stacked benzene

molecules," Chemical Physics, DOI:10.1016/j.chemphys.2015.03.006.

POSTERS



Modelling of carbon nanoparticles adsorbed on graphene

V. Krasnenko1,*, A. Tamm1, V. Boltrushko1, A.-L. Peikolainen2, J. Kozlova1, K. Kukli1, V. Hizhnyakov 1

1University of Tartu, Institute of Physics, Department of Materials Science, Riia 142, EE-51014 Tartu, Estonia,

2IMS Lab, Institute of Technology, University of Tartu, Nooruse 1, EE-50411 Tartu,Estonia

* [email protected]

Zirconium oxide films on CVD graphene using carbon nanoparticles as an adhesion layer between graphene and metal oxide were prepared and investigated. Carbon nanoparticles are found to form a heterogeneous interface which promotes growth of films on graphene in low temperature atomic layer deposition process. From experimental data it follows that the nanoparticles initially consist of graphite-like nanocrystallites bound on graphene without noticeable distortion of the latter. We present here a model of nanocrystallites on graphene. In this model the C6 planes of the crystallite are tilted with respect to graphene sheet. Two different tilted orientations of the crystallites are found to be possible: 1) the C6 planes of the crystallite are tilted to the angle 48° or 2) to the angle 70° with respect to the graphene sheet. The described structures have mutually orthogonal tilting directions. From experiment data the C-nanoparticles on graphene covered by zirconium oxide layers confirm the existence of tilted structures with the given angles, where the crystallographic orientation of the ZrO2 may be influenced by local forces of carbon nanoparticles on graphene. Although we cannot see directly the layered structure of the carbon nanoparticles, the structure of surrounding ZrO2 can be clearly detected. To better understand the properties of the described structures we performed numerical modelling of them using the Density Functional Theory based methods.

POSTERS



Dynamics of magnetic field penetration into the conducting magnet

B. Ducharne1, G. Sebald1, D. Guyomar1, G. Litak2,*

1Institut National des Sciences Appliquees de Lyon, 69621 Villeurbanne cedex, France 2Lublin University of Technology, Nadbystrzycka 36, PL-20-618 Lublin, Poland

* [email protected]

We propose an approach to solve the coupled problem of the magnetic field penetration into the conducting magnet and a frequency dependent magnetic hysteresis [1]. The magnetic field diffusion is related to the macroscopic eddy currents and the hysteresis model to the microscopic eddy currents derived from the magnetic domain wall movements. Basing on a lump model and fractional derivative operators we demonstrate how using fractional operators is possible to replace the coupled diffusion/dynamic hysteresis in a simplest formulation which can be solved easily. We confirm the model using experimental available information, obtained by the standard single sheet tester measuring bench.

1. G..Sebald, E..Boucher,.D. Guyomar, "A model based on dry friction for modeling hysteresis

in ferroelectric materials", J. Appl. Phys. 96, 2785 (2004).

POSTERS



Transverse intrinsic pseudo-local modes in monatomic chain and graphene

M. Klopov1, A. Shelkan2, V. Hizhnyakov2,* 1Technical University of Tallinn

2Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia * [email protected]

At present it is already well known fact that in perfect nonlinear lattices may exist

localized vibrations, called as “intrinsic localized modes” (ILMs) or discrete breathers. In numerical studies of ILMs different two body potentials have been used. All of these potentials have strong odd anharmonicities causing softening of potentials with increasing the energy. The ILMs found in these studies, always drop down from the optical band(s) into the phonon gap, if there is one. However in some metals (Ni, Nb, Fe, Cu) and dielectrics (Ge, diamond) the pair potential approximation is insufficient; due multi-particle interactions the odd anharmonicities here are reduced resulting in appearance of ILMs with the frequencies above the phonon spectrum [1,2].

There are also cases when odd anharmonicities totally disappear due to symmetry arguments. An example is given by the linear chains where this happens for transverse vibrations. Therefore one can expect that in chains may exist localized transverse anharmonic modes with the frequencies above the maximum frequency of transverse phonons T .

Usually T L , the maximum frequency of longitudinal phonons; i.e. the mode falls in

resonance with these phonons and decay. However the decay is slow due to weak interaction of transversal and longitudinal vibrations. This long-living localized transverse vibration we call as the intrinsic pseudolocal mode (IPLM) in analogy with similar modes associated with point defects. Our calculations of the stretched monatomic chain with Morse pair-potential fully confirm this conclusion: using typical for metallic atoms Morse potential we have found for 5% stretching the transverse IPLM which decays less than 0.1% for 1000 periods of vibrations.

Another example is given by planar atomic structures, such, e.g. as graphene where also odd anharmonicities of transverse vibrations disappear. The maximum frequency of transverse acoustic phonons in graphene (16 THz) is also much smaller than that of longitudinal phonons (49.5 THz). Therefore here one can also expect the existence of IPLMs with the frequency above the spectrum of transverse phonons. We performed numerical modelling of vibrations of graphene using LAMMPS with AIREBO potentials and indeed have found long-living transverse IPLMs. E.g. an even transverse IPLM with the amplitude of the central atom 0.4 Å has the frequency 23.7 THz and decays less than 1% for 10 ps (i.e. for more than 400 periods).

1. Haas, M., Hizhnyakov, V., Shelkan, A., Klopov, M., Sievers, A.J.: Prediction of high-

frequency intrinsic localized modes in Ni and Nb. Phys. Rev. B 84, 144,303(1–8) (2011). 2. V. Hizhnyakov, M. Haas, A. Shelkan, M. Klopov, Theory and molecular dynamics

simulations of intrinsic localized modes and defect formation in solids, Phys. Scr. 89, 044003 (2014).

POSTERS

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POSTERS



Peculiarities of the angle-resolved photoemission line shape analysis for strongly correlated electron systems

E.I. Shneyder1,*, S.G. Ovchinnikov1, A.A. Kordyuk2

1 Kirensky Institute of Physics, 50/38 Akademgorodok, Krasnoyarsk, 660036, Russia 2 Institute of Metal Physics of National Academy of Sciences of Ukraine, 03142 Kyiv, Ukraine

* [email protected]

We argue that the momentum asymmetry observed [1] in the photoemission spectra of high-Tc cuprates has, among other things, the fundamental reason and can reflect the strength of the electron correlations [2]. The additional odd momentum contribution to the spectral function results from the general structure of the Green’s function of quasiparticles in strongly correlated systems. In the atomic limit the latter is defined not only by the self-energy of quasiparticles but also by a strength operator [3].

The odd contribution to the momentum distribution curve (MDC) may be found experimentally in the underdoped samples of other cuprates that are close to the doped Mott-Hubbard insulator and in optimally doped ones where correlation effects are still strong enough. In overdoped cuprates as well as in Fe pnictides, the electron correlations are not so strong, hence an odd contribution is not expected.

We believe that the general structure of the Green’s function in correlated systems should be a reference point in experimental data analyses. Recently the improved phenomenological version of extremely correlated Fermi-liquid (ECFL) model has been suggested [4]. This theory successfully describes the ARPES data of high-Tc materials including MDC asymmetry. We reveal that all modifications of the spectral function in the framework of the ECFL model can be combined into a single one. It turns out that the structure of such a universal spectral function is fully consistent with the structure of spectral function obtained from the general consideration.

(*) This work is supported by the Russian scientific foundation, the grant 14-02-00061. 1. K. M. Shen, F. Ronning, D. H. Lu, F. Baumberger, N. J. C. Ingle, W. S. Lee, W. Meevasana,

Y. Kohsaka, M. Azuma, M. Takano, H. Takagi, and Z.-X. Shen, “Nodal Quasiparticles and Antinodal Charge Ordering in Ca2-xNaxCuO2Cl2”, Science 307 (5711), 901-904 (2005).

2. S.G. Ovchinnikov, E.I. Shneyder, A.A. Kordyuk, “General analysis of the angle-resolved photoemission line shape for strongly correlated electron systems”, Phys. Rev. 90 (22), 220505-1 – 220505-5 (2014).

3. S. G. Ovchinnikov and V. V. Val’kov, Hubbard Operators in the Theory of Strongly Correlated Electrons, ISBN 1-86094-430-2, Imperial College Press, London, (2004).

4. Kazue Matsuyama and G.-H. Gweon, Phenomenological Model for the Normal-State Angle-Resolved Photoemission Spectroscopy Line Shapes of High-Temperature Superconductors, Phys. Rev. Lett. 111 (24), 246401-1 – 246401-5 (2013).

POSTERS



The spin-1 J1-J3 Heisenberg model on a triangular lattice

P. Rubin1,*, A. Sherman1, M. Schreiber2 1Institute of Physics, University of Tartu, Ravila 14 c, 50411 Tartu, Estonia

2Institut für Physik, Technische Universität, D-09107Chemnitz, Germany * [email protected]

Motivated by the experimental data for NiGa2S4, the spin-1 Heisenberg model on a triangular lattice with the ferromagnetic nearest- and antiferromagnetic third-nearest-neighbor exchange interactions, J1 = - (1-p)J and J3 = pJ, J > 0, is studied in the range of the parameter 0 ≤ p ≤ 1. Mori's projection operator technique is used as a method which retains the rotation symmetry of spin components and does not anticipate any magnetic ordering. For zero temperature several phase transitions are observed.

At p ≈ 0.2 the ground state is transformed from the ferromagnetic spin structure into a disordered state, which in its turn is changed to an antiferromagnetic long-range ordered state with the incommensurate ordering vector Q ≈ (1.16, 0) at p ≈ 0.31. With growing p the ordering vector moves along the line Q - Q1 to the commensurate point Q1 = (2π/3, 0) which is reached at p = 1. The final state with an antiferromagnetic long-range order can be conceived as four interpenetrating sublattices with the 120˚ spin structure on each of them. The model is able to describe the state with the incommensurate short-range order observed in NiGa2S4. Also our approach is able to reproduce a quadratic temperature dependence of the specific heat and dependence of the uniform spin susceptibility on T in NiGa2S4.

To verify the used approach the ground state energy and corresponding spin-spin correlations for small lattices are compared with exact-diagonalization results obtained with the SPINPACK code (the Lanczos exact diagonalization). The Mori’s and the Lanzcos results are in qualitative agreement.

POSTERS



Electron dynamics and inhomogeneous quantum quenches - overcoming the small-amplitude limit

E. von Oelsen*, G. Seibold

Institute for Physics and Chemistry, BTU Cottbus - Senftenberg, Germany * [email protected]

We make use of the recently developed time-dependent Gutzwiller theory [1,2] in order to

study the dynamics of interacting electrons after sudden quenches (“quantum quench”) of the Coulomb interaction strength and the local on-site potential in the Hubbard model. Our approach allows for a detailed study of both density-matrix elements and double occupancy as a function of time. The formalism is not limited to small amplitudes or homogeneous systems, but is rather general.

In our calculations, we look for the dependence of the electrons' dynamic on the strength of the quench. Our results reproduce the small-amplitude limit, but yield small corrections for strong quenches. Additionally, we investigate the long-time behavior of the different Fourier modes in case of single-site quenches. We study the energy distribution over the different Fourier components and find qualitatively different results compared to a time-dependent Hartree-Fock calculation.

1. “Linear-Respone from the Time-Dependent Gutzwiller Approximation”, J. Bünemann, M.

Capone, J. Lorenzana, G. Seibold, New J. Phys 15 (2013) 053050. 2. “Quantum quenches in the Hubbard model: Time-dependent mean-field theory and the role of

quantum fluctuations”, M. Schiro, M. Fabrizio, Phys. Rev. B 83 (2011) 165105

POSTERS



Strong-coupling diagram technique for strong correlations

A. Sherman


In recent years, in connection with the discovery of iron-based superconductors and investigations of the influence of electron correlations on topological insulators, the interest has increased in the multi-band generalizations of the Hubbard model. For these model Hamiltonians it would be desirable to find an approach, which, being comparatively simple computationally, yields at least qualitatively correct results. As a possible candidate for such an approach the strong coupling diagram technique is considered in this work. The method is based on the expansion in powers of the kinetic energy. The elements of diagrams are on-site cumulants of creation and annihilation operators and hopping lines connecting cumulants on different sites. Despite the fact that by the construction the approach is intended for the strong coupling case, it gives the correct result for vanishing Hubbard repulsions U. The approach leads to a set of equations for the electron Green’s function, which can be self-consistently solved. At half-filling, for the semi-elliptical density of states (DOS) as well as for the two-dimensional t-U and t-t’-U models these equations describe the Mott transition, which occurs at 7 8cU with the bandwidth. This value is close (identical for the semi-elliptical

DOS) to that obtained in the Hubbard-III approximation. By the positions of maxima, shapes and their variation with momentum and electron concentration n the calculated spectral functions are close to results of Monte Carlo simulations in the range 0.7<n<1.3. Also the variation of the momentum dependence of occupation numbers with U is in satisfactory agreement with Monte Carlo data at half-filling. The behavior of the Mott gap is different in the t-U and t-t’-U models [1].

1. A. Sherman, Physica B 456, 35 (2015); Int. J. Mod. Phys. B 29, 1550088 (2015); arXiv:

1501.03587.

POSTERS



47,49Ti NMR study of spin-Peierls compound TiPO4

A. Leitmäe*, I. Heinmaa, E. Joon, A.A. Tsirlin and R. Stern

National Institute of Chemical Physics and Biophysics Akadeemia tee 23, Tallinn, 12618, Estonia * [email protected]

We have performed a detailed study of 47Ti and 49Ti NMR on a single crystal TiPO4

sample with the aim to learn about the local structure surrounding titanium ions. The Ti lattice site occupies the center of an axially compressed octahedron and its ground state is a non-bonding dxy orbital, where x and y axes are pointing towards the nearest oxygen sites in the equatorial plane of octahedron and z is parallel to the compressed axis. According to Hund’s rule, this state is filled with a single electron carrying spin S= ½, so at high temperatures TiPO4 is a paramagnetic insulator. At low temperatures the Ti sites, which are sitting in a quasi-1D Heisenberg chain, dimerize and form the singlet ground state with S=0 [1]. This state arises through two phase transitions Tc1=111K and Tc2=74K with an incommensurate phase in-between. Experimentally determined principal components and the orientation of the electric field gradient tensor at the Ti site are basically the same at both high and low temperature phases with minor changes due to phase transitions and local crystalline symmetry transformations. This means that the orbital dxy of the Ti ion is the ground state in a paramagnetic and also the spin-Peierls phase. The calculated electric field gradient tensor, within the accuracy of the theoretical model applied, is in good accordance with the experimental data.

1. Spin-Peierls transition in the S=1/2 compound TiPO4 featuring large intrachain coupling. J. M.

Law, C. Coch, R. Glaum, I. Heinmaa, R.Stern, J. Kang, C. Lee, M.-H. Whangbo, R. K. Kremer – Phys. Rev. B 83, 180414(R) (2011).

POSTERS



Shrinking of the fluctuation region in a two-band superconductor

A. Vargunin*, T. Örd

Institute of Physics, University of Tartu, Tartu, EE-50411, Estonia * [email protected]

In a two-band superconductor, two qualitatively different fluctuation modes related to the gap modules contribute to the free energy and heat capacity, together with the phase fluctuations. The first mode has divergent temperature behavior since it accounts for critical fluctuations around the phase transition point, Tc, along with pseudo-critical ones associated with the former instability of the weaker superconductivity component. The involvement of these two factors, competing under interband interaction, results in a Ginzburg number that varies with Tc non-monotonically, allowing a reduction of up to 75%. This makes the fluctuations effective in revealing additional superconducting components in the system. The second mode does not diverge, but has a jump at Tc, defined uniquely by the strength of the interband interaction. This mode contributes fundamentally beyond the critical domain [1].

1. A. Vargunin, T. Örd, "Shrinking of the fluctuation region in a two-band superconductor",

Supercond. Sci. Technol. 27 085006 (2014).

POSTERS



Multiband superconductivity with different band pair compositions

N. Kristoffel*, P. Rubin

Institute of Physics, University of Tartu, Ravila 14 c, 50411 Tartu, Estonia * [email protected]

Interband pairing interaction plays a significant role in multiband superconductivity. Interaction channels creating the pairs of intraband (a) and interband (b) composition can appear. Simultaneous action of these channels is investigated. A three band model where two similar bands interact with strength Wa and Wb with the itinerant d-band has been proposed. The mean field Hamiltonian incorporates three order parameters genetically associated with these dispersive bands. The quasiparticle energies and the nonlinear system for the coupled order parameters have been found.

Illustrative calculations have been made for various coupling strengths, chemical potential position and temperature. Two parallel solutions can appear for the same parameter set. Appointments to the presence of metastable extrema in the free energy have been found. The pairing channels with intra- and interband pairs compete. Separated or jointed couples of gap temperature dependences from the different channels can appear. The effect of release of one channel characteristics when the ones of the other vanish has been traced in various realizations. Above such a temperature the gap characteristics of the other channel follow the dependences as the first channel was logged out. The a- and d-band gaps initiated by Wa

appear together and vanish on a common temperature. The enhancement of |Wb| suppresses the larger of them more. The general nature of the gaps vs temperature is quite sensible to the ratio Wa/Wb. There can be situations where besides the normal behaviour of gaps vs temperature, when a Tc can be determined also “bubbles” appear. The latter are built up from the components of different parallel solutions. Enhancement of attractive Wb leads to higher temperatures for “bubble” rupture. This change is of critical nature. When the bubble closes its components of barrier and cavity nature joint and the free energy extremum is washed out.

(*) This work was partially supported by the European Union through the European Regional Development Fund.

POSTERS



Temperature dependent sizes of the Cooper pairs in a BCS-type two-band superconductor

T. Örd1,*, K. Rägo1, A. Vargunin1, G. Litak2 1 Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia

2 Lublin University of Technology, Faculty of Mechanical Engineering, Nadbystrzycka 36, PL-20618 Lublin, Poland

* [email protected]

In this study, the temperature variation of the mean sizes of the Cooper pairs of two-gap

superconductors has been examined. We define the mean sizes of the Cooper pairs in a BCS-type two-band superconductor

21

2

22

d

d

rr

rrrC

by means of the temperature dependent Cooper pair wave functions

2121 exp rrkiaarrk

kk

,

where 1,2 is the band index. In the one-band weak-coupling limit the mean size of the

Cooper pair decreases moderately (about 20%) if temperature increases from 0 to CT .

However, in a two-band BCS-type model with interband pair-transfer interaction the decrease of one of C may be substantially stronger. The observation is related to the circumstance

that in two-gap superconducting systems one of the ratios | (0) | / B Ck T may be noticeably

smaller compared to the corresponding one-band BCS universal value 1.76. This situation appears first of all if (i) intraband superconductivity coupling in one band is substantially weaker compared to another and (ii) interband coupling is very weak, i.e. the well-pronounced interband proximity effect is present. It was also found for the certain values of parameters of a two-band model that the mean size of the Cooper pair can increase with temperature and it can pass through a maximum.

We analyse also the spatial behaviour of the Cooper pair wave functions in dependence on the system parameters and temperature.

(*) The research was supported by the European Union through the European Regional Development Fund (Centre of Excellence "Mesosystems: Theory and Applications", TK114).

POSTERS



Leaky Dyakonov surface plasmon polaritons

A. Loot


Surface plasmon polaritons (SPPs) at metal-dielectric interface has attracted a lot of scientific interest in the last three decades and has many useful/potential applications in sensing, signal enhancement, nonlinear optics, etc. Another type of surface waves (SWs) are Dyakonov waves (DWs), which propagate at the interface of isotropic and anisotropic medium [1]. This work is focused to the combination of the SPPs and DWs – the Dyakonov SPPs (DSPPs) at the interface of metal and anisotropic crystal are theoretically studied.

The properties of DSPPs at the interface of metal – positive uniaxial crystal were studied by the dispersion relationship derived by M. I. D’yakonov [1]. It was shown, that if the condition

/ ,e m (1) where / 1,e o m is the dielectric permittivity of the metal, ,o m are the ordinary and

extraordinary permittivities of the crystal, is met, then the wave becomes leaky. It is shown, that only the extraordinarily polarized component in the crystal could become leaky and we name such half-leaky SW to leaky DSPPs (LDSPPs). To understand the properties and usefulness of LDSPPs they were theoretically studied in Kretschmann configuration by general 4x4 transfer matrix method [2]. Under proper excitation the structure consisting of ZnSe prism, 60nm thick silver film, KTP crystal could transmit over 40 % of incident light

(the transmission of the silver film itself is less than 1 %). Such extraordinary transmission is accounted to the resonant energy transfer from incident light to LDSPPs and then to the anisotropic crystal as extraordinary wave.

In addition, it is possible to discard the Kretschmann prism completely. As the LDSPPs are leaky, then it is possible to excite the SWs just by extraordinarily polarized wave through the crystal without the coupling prism. Such simple 2 layer system supporting SWs and with built-in excitation mechanism could be extremely useful in the experiments of nonlinear and quantum optics, where high field enhancement of SWs are required. For example LDSPPs could simplify the experimental setup of the SPP-enhanced spontaneous parametric down conversion by eliminating the need of immersion oil layer between the prism and metal film, which inhibits the experimental realization by low refractive index (< 1.8) and high absorption near UV [3].

1. M. D’yakonov, “New type of electromagnetic wave propagating at an interface”, Sov. Phys.

JETP, 67 (4), 714–716 (1988). 2. I. J. Hodgkinson, S. Kassam, and Q. H. Wu, “Eigenequations and Compact Algorithms for

Bulk and Layered Anisotropic Optical Media: Reflection and Refraction at a Crystal-Crystal Interface”, J. Comput. Phys., 133 (1), 75–83 (1997).

3. Hizhnyakov, V. and Loot, A., “Spontaneous down conversion in metal-dielectric interface - a possible source of polarization-entangled photons”, arXiv:1406.2174 [quant-ph], (2014).

POSTERS



Time dependent theory of two step absorption of two pulses

I. Rebane

Institute of Physics, University of Tartu, Ravila 14c, Tartu 50411, Estonia [email protected]

The time dependent theory of two step absorption of two different light pulses with arbitrary duration in the electronic three-level model is proposed. The probability that the third level is excited at the moment t is found in depending on the time delay between pulses T, the spectral widths of the pulses Δ1 and Δ2 and the energy relaxation constants γ0, γ1 and γ2

of the electronic levels 0, 1 and 2. The time dependent perturbation theory is applied. In the calculations the pulses are taken as coherent and of a single-sided exponential

shape, ω1 and ω2 are the frequencies of the maximums, 0 and T are the time moments when the pulses begin to pass through the impurity center. The resonance conditions are ω1 ≈ Ω01 and ω2 ≈ Ω12 where Ω01 and Ω12 are the frequencies of the transitions 0→1 and 1 →2.

In the general case, where the spectral widths of the pulses Δ1and Δ2 are comparable with the energy relaxation constants γ1 and γ2, two lines exist in the both cases (at the fixed value of ω1 - Ω01 (case A) or at the fixed value of ω2 - Ω12 (case B)): the line with the maximum at ω2 = Ω12 (A) (or the line with the maximum at ω1 = Ω01 (B)) and the line with the maximum at ω2 = Ω01 + Ω12 - ω1 (A) ) (or the line with the maximum at ω1 = Ω01 + Ω12 - ω2 (B)).

In the special case of very long pulses (Δ1 ≈ Δ2 ≈ 0) the developed theory gives the same results as in [1].

(*) This work was supported by the European Union through the European Regional Development Fund (Centre of Excellence "Mesosystems: Theory and Applications", TK114).

1. M. Tanasittikosol, C. Carr, C.S. Adams, K.J. Weatherill, "Subnatural linewidths in two-photon

excited-state spectroscopy ", Phys.Rev. A 85, 033830-1–033830-8 (2012).

POSTERS



Optical manifestations of energy relaxation in quasi-degenerate electronic states

T. Vaikjärv

Institute of Physics, Ravila 14c, Tartu, Estonia [email protected]

Excited states in molecules and impurity centers in crystals with high symmetry are

usually degenerate. The dynamics which occurs in the vicinity of the symmetric configuration is essentially determined by the nonadiabaticity of the electronic and nuclear motion. We present a method which allows one to study theoretically the dynamics of the time evolution of the excited states of these systems. We note that the phonon continuum in the excited state is taken into account.

Our study is based on the recently proposed method [1] of calculation of optical transitions in centers with the Jahn-Teller and pseudo-Jahn-Teller effect in the final state. The time evolution of the states is calculated in the density matrix form using the master equation [2]. The result of this work is calculated evolution of the relaxation process [3]. The method is applicable for calculations for short and intermediate times as well as long times. The most interesting thing to notice is the dependence of relaxation times on the distance of nearest neighbor vibronic states.

1. K.Pae, T. Vaikjärv, V. Hizhnyakov Program & Abstracts: 20th International Symposium on

the Jahn-Teller Effect (2010) 77-79. 2. G. Lindblad, Commun. Math. Phys. 48 (1976) 119. 3. T. Vaikjärv, V. Hizhnyakov, J. Chem. Phys. 140 (2014) 064105.

POSTERS



Directional dichroism of THz radiation in multiferroic Sr2CoSi2O7

J. Viirok

National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn, 12618, Estonia [email protected]

POSTERS



Fermi excitations in doped helium-3 droplets probed by Raman scattering

I. Tehver1,*, G. Benedek2,3, V. Hizhnyakov1

1Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia 2Donostia International Physics Center (DIPC) and University of the Basque Country (EHU),

Paseo de Lardizabal 4, 20018 Donostia/San Sebastian, Spain 3Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca,

Via Cozzi 53, 20125 Milano, Italy [email protected]

Light scattering in quantum liquid helium-3 may involve a unique mechanism - the creation and annihilation of atom excitations across the Fermi level [1,2]. The density of states of particle-hole excitations in the low-energy limit is strongly enhanced as compared to that of collective excitations of phonons in helium-3. This makes possible to directly observe Fermi excitations in the resonant Raman scattering (RRS) by 3He droplets doped by impurity molecules. The RRS spectra essentially depend on the excitation frequency. In case of excitation in the anti-Stokes side of absorption the first order RRS is directly determined by the particle-hole excitations in the vicinity of the impurity molecule and the contribution of phonons mainly given by the localized spherical vibration. The calculations are made for a 3He droplet doped by a glyoxal molecule.

1. G. Benedek and V. Hizhnyakov, “Fermi sea excitations in the optical spectrum of a doped

3He droplet”, Chem. Phys. Lett. 548, 17-22 (2012). 2. G. Benedek, V. Hizhnyakov, J. P. Toennies, “The response of a 3He Fermi liquid droplet to

vibronic excitation of an embedded glyoxal molecule”, J. Phys. Chem. A 118, 6574−6583 (2014).

POSTERS



Enhanced dynamical Casimir effect for surface and guided waves

V. Hizhnyakov*, A. Loot, S.Ch. Azizabadi


Surface plasmon polaritons (SPPs) and guided dielectric waves have strongly enhanced field. This is important for weak optical processes which otherwise are difficult to observe. Here we consider the possibility to use these waves for enhancement of spontaneous emission of pairs of quanta of electromagnetic excitations in a resonator when its optical length changes in time under laser excitation. This emission is called as the dynamical Casimir effect (DCE).

In the planar interface the DCE-induced electromagnetic quanta are emitted by pairs with the wave vectors ( , )x y

and ( , )x y

and frequencies , 0 . The

spectrum is continuous with the maximum at 0 2 . The rate of emission is determined

by the dimensionless parameter 0 02v a [1,2], where 2

0 0 0

(2) I Za is the amplitude

of oscillations of the optical length, (2) is the second-order nonlinear susceptibility, is the

enhancement of the field, 0 02 c , 0 and 0I are the laser frequency and intensity, 0Z

is the impedance of the free space. For weak excitation 1 and the yield of emission of

SPP quanta is [3] 22 4 2 (2) 3

0 0 0 010 2l Z ( 0l is the length of resonator). For 60 10I

W/m2 and 20 (typical value) 310v and 710 . However for long-range SPPs one

gets 210 and 1v already for 50 10I W/m2. In this case the theory [3] is not applicable.

Here we present a theory of DCE which works also for 1v . We have found that the

spectral rate of emission forward by unit width of the interface equals 22 2 2 *

0( ) 2 1 ( ) (1 )(1 )I v v G G

where 1( ) 2 2 ln (1 ) (1 )G i , 0 . For 2.9v the emission is

resonantly enhanced at 0 2 . The dependence of log I on v and the angle of emission

is given on Fig.1. The enhancement may exceed few orders of magnitude.

Fig. 1. The rate of emission due to DCE for surface plasmon

polaritons and guided dielectric waves: dependence log I on

0v I , and , where 0I is the intensity of laser light, is the

direction of emission.

1. G.T. More, Quantum theory of the electromagnetic field in a variable length one dimensional cavity, J. Math. Phys. 11 (1970) 2679.

2. V. Hizhnyakov and H. Kaasik, "Dynamical Casimir effect: quantum emission of a medium with timedependent refractive index," in Northern Optics 2006, Bergen, Norway, 2006.

3. V. Hizhnyakov, A. Loot, S.Ch. Azizabadi, Dynamical Casimir effect for surface plasmon polaritons, Physics Letters A , 379 (2015) 501–505.

v

log( )I

POSTERS



Light propagation in metal-coated SNOM tips: experiment and numerical simulations

V. Palm*, A. Loot, M. Rähn, J. Jäme, V. Hizhnyakov


The mesoscopic effect of spectral modulation (MSM) can be observed for a light transmitted by a multimode fiber terminated with a SNON tip due to the interference of at least two remaining photonic modes at the exit [1]. Using a MSM-based two-mode experimental technique, the modal dispersion has been studied for several SNOM tips coated with Cr and Al metal layers of thickness 20 and 200 nm respectively [2,3]. This modal dispersion turned out to be of much higher magnitude and of the opposite sign compared to the inherent modal dispersion of the fiber tail, which was attributed to a mode-selective coupling of photons to surface plasmons of the metal coating [2,3]. A tentative assumption was made that replacing the Al layer with an Au layer should further increase the plasmonic coupling and its effect on the modal dispersion in a SNOM tip. Nevertheless, our new experimental results with a Cr/Au-coated SNOM tip did not show any dramatic change compared to Cr/Al-coated SNOM tips.

In order to get an insight on the propagation of electromagnetic excitations in our SNOM tips, we initiated numerical simulations based on the theory outlined by Novotny and Hafner [4]. Some initial results of the ongoing efforts will be presented. According to our tentative conclusion, a thin (20 nm) Cr layer appears to play the main role for different modes of surface plasmon polariton waves generated on its interface with the fused silica of the fiber. Typically, only a subtle part of the electromagnetic energy reaches the outer metal layer, which explains its small influence on the modal dispersion observed for the SNOM tips.

1. M. Rähn, M. Pärs, V. Palm, R. Jaaniso, V. Hizhnyakov, "Mesoscopic effect of spectral

modulation for the light transmitted by a SNOM tip", Opt. Commun. 283 (11), 2457-2460 (2010).

2. V. Palm, M. Rähn, V. Hizhnyakov, "Modal dispersion due to photon-plasmon coupling in a SNOM tip ", Opt. Commun. 285 (21-22), 4579-4582 (2012).

3. V. Palm, M. Rähn, J. Jäme, V. Hizhnyakov, "Mesoscopic effect of spectral modulation for the light transmitted by a SNOM tip", Proc. SPIE 8457 (84572S), 1-10 (2012).

4. L. Novotny, C. Hafner, “Light propagation in a cylindrical waveguide with a complex, metallic, dielectric function”, Phys. Rev. E 50 (5), 4094-4106 (1994).

POSTERS



Semi-microscopic theory of thickness dependences of the forbidden (optical) gap and of the refractive index

in PMMA type systems with structural ordering polar groups

P. Konsin*, B. Sorkin

Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia * [email protected]

The influence of the structural order of polymethylmethacrylate (PMMA) type films on

the refractive index n and optical (forbidden) gap gE is studied theoretically. We have

developed further the vibronic (electron-phonon) theory of the ferroelectrics [1-6] with strong electron-lattice interaction to calculate the quantum size effect. For the first time the size effects in the vibronic theory are considered in [7]. We obtained the formulae for the optical properties of PMMA type films. The theory is compared with the experimental data of PMMA films [8,9]. The dependences )(LEg for film thicknesses nmLnm 7020 in the

electric field and in the absence of the field are predicted in this report. 1. P. I. Konsin and N. N. Kristoffel, in: Interband Model of Ferroelectrics, eds. E. V. Bursian, Y.

Girshberg (Hertzen Pedagogical Institute, Leningrad, 1987), p. 32. 2. N. Kristoffel and P. Konsin, Phys. Stat. Sol. B 149(1), 11-40 (1988). 3. I. B. Bersuker, The Jahn-Teller Effect (Cambridge University Press, Cambridge, 2006). 4. M. E. Lines and A. M. Glass, Principles and Application of Ferroelectrics and Related

Materials (Clarendon Press, Oxford, 1977). 5. P. Konsin and N. Kristoffel, Ferroelectrics 226, 95 (1999). 6. P. Konsin and B. Sorkin, Ferroelectrics 359, 63 (2007). 7. P. Konsin, Phys. Stat. Sol. B 100, K59 (1980). 8. O. Lyutakov, I. Huttel, and V. Švorčik, J. Mater. Sci. Mater. Electron, 18, 457 (2007). 9. V. Švorčik, O. Lyutakov, and I. Huttel, J. Mater. Sci. Mater. Electron, 19, 363 (2008).

POSTERS



Model of band tail absorption saturation with fs pulses

R. Laasner1,*, V. Nagirnyi1, S. Vielhauer1, V. Sirutkaitis2, R. Grigonis2

1Institute of Physics, University of Tartu, Ravila 14c, Tartu 50411, Estonia 2Laser Research Center, Vilnius University, Vilnius 2054, Lithuania

* [email protected]

We have studied the luminescence decay kinetics of the CdWO4 scintillator crystal using 100-fs laser pulses with sub-band-gap excitation energies (the Urbach tail region). Phonon-assisted absorption, generally the accepted mechanism of absorption in the Urbach tail, cannot be applied with fs pulses, i.e., when the pulse duration is shorter or comparable to the period of optical phonons. Instead, absorption is determined by the limited number of centers with an atomic configuration capable of absorbing a photon at the moment of excitation. For a sufficiently high excitation density, this leads to absorption saturation.

The saturation effect, which takes place during the very short excitation stage, influences the luminescence stage, where the nonlinear interaction between excitations is dependent on the initial distribution of excitations. In CdWO4 and similar crystals, this refers to the dipole-dipole interaction of excitons responsible for the luminescence quenching. We have developed a model that allows the estimation of the saturation density of excitations from the shape of the luminescence decay curves [1]. The model is applicable to excitonic intrinsic scintillators.

We have shown the saturation effect to be present only in the Urbach tail and not in the fundamental absorption region, which conforms to the basic assumptions of the model. Furthermore, since the number of centers capable of absorption at the moment of excitation is correlated with the phonon distribution, the saturation effect is expected to be temperature dependent. We have shown that at 4.2 eV excitation (optical gap ~4.8 eV), in the temperature range 78-400 K, the saturation density in CdWO4 changes from the order of 1018 cm-3 to the order of 1019 cm-3, which confirms the nature of the saturation effect.

1. R. Laasner et al., J. Phys.: Condens. Matter 25, 245901 (2013).

POSTERS



Surface transverse Abraham force exerted on a vortex wave packet during its reflection and refraction at a plane interface

V.G. Fedoseyev

Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia [email protected]

The process of reflection and refraction of a paraxial e.-m. wave packet at a plane

interface of two isotropic transparent media is considered. It is assumed that the packet is linearly polarized and its intrinsic orbital angular momentum (IOAM) is well defined. Again, it is assumed that the incident packet is situated far enough from the interface at an initial instant of time 0t and moves quasi-freely during some time interval. The coordinate, which is

perpendicular to the trajectory of the motion of this packet in the quasi-free regime and to the normal to the interface, is called the transverse coordinate TRx .

In order to analyze the packet’s evaluation, the Abraham energy-momentum tensor is employed. The motion of the center of gravity of the total electromagnetic field ( )tR is

considered; a relation between the second derivative 2 2( ) /d t dtR and the sum of the stress

force and the Abraham force is established. It is shown that the transverse component of the former is equal to zero at any t . Hence, one can conclude that it is the transverse Abraham force which is responsible for the change of ( )TRR t . It is pointed out that this force can

sufficiently differ from zero only during the time intervals, when the leading and trailing fronts of the incident packet are transformed on the interface. The magnitude of the impulse of the transverse Abraham force TRI , produced during the former interval, is approximately

equal to the magnitudes of such an impulse, produced during the latter one, while the signs of these impulses are opposite.

When the time interval 0t t is long enough, the secondary beams are situated far enough

from the interface at t . It is shown that at such an instant the difference 0( ) ( )TR TRR t R t is

equal, if some additional conditions are fulfilled, to the sum of the IOAM-dependent transverse shifts of the centers of gravity of the reflected and refracted beams weighted by the reflectance and transmittance, respectively. A quantitative relation between these shifts and the impulse TRI is established, and, on the basis of this relation, the value of TRI is calculated.

The global character of this quantity is pointed out: TRI is proportional to the azimuthal index

of the incident beam and is not dependent on any other characteristics of it.

Author index

A

Archilla, J.F.R. 14, 23 Auret, F.D. 14, 23 Azizabadi, S.Ch. 74

B

Babaev, E. 22 Baldini, E. 21 Barabanov, A.F. 29 Benedek, G. 73 Benfatto, L. 31 Bezuglova, G.S. 25 Bianconi, A. 19 Boltrushko, V. 56, 57 Braun, H. 39 Brenig, W. 33 Büchner, B. 18 Bussmann‐Holder, A. 11

C

Carbone, F. 20, 21 Caslin, K. 11, 16 Castellani, C. 31 Chechin, G.M. 25, 37 Chergui, M. 20 Coelho, S.M.M. 14, 23 Concistrè, M. 51

D

Darinskii, A.N. 38 Decurtins, S. 13 Dmitriev, S.V. 25, 36 Dubinko, V.I. 14, 34 Ducharne, B. 58

F

Fedoseyev, V.G. 78

G

Gabovich, A.M. 47

Garaud, J. 22 Gavrichkov, V.A. 28 Gordon, E. 16 Grigonis, R. 77 Guyomar, D. 58

H

Haas, M. 55 Han, H. 38 Hanfland, M. 16 Heinmaa, I. 17, 45, 65 Heinsalu, E. 24 Hizhnyakov, V. 14, 54, 57, 59, 73, 74, 75 Hovhannisyan, M. 39 Hüvonen, D. 49

J

Jäme, J. 75 Joon, E. 17, 45, 65

K

Kagan, M.Yu. 29 Kalda, J. 27 Karatsuba, E.A. 50 Kaski, K. 35 Klokishner, S.I. 13 Klopov, M. 53, 59 Kluge, M. 39 Köhler, J. 11 Konsin, P. 76 Kordyuk, A.A. 61 Korshunov, M.M. 28 Korznikova, E.A. 36 Kosevich, Yu.A. 38 Kozlov, P.A. 42 Kozlova, J. 57 Krachmalnicoff, A. 51 Krasnenko, V. 56, 57 Kremer, R.K. 11, 16 Kristoffel, N. 67 Kugel, K.I. 29 Kukli, K. 57


80 Author index

Kuronen, A. 35 Kuz’min, V.I. 30

L

Laasner, R. 77 Lei, X. 51 Leitmäe, A. 45, 65 Letz, M. 39 Levitt, M.H. 51 Li, M.S. 47 Li, Y. 51 Litak, G. 46, 58, 68 Liu, S.X. 13 Lobzenko, I.P. 25 Loot, A. 69, 74, 75 Lorenzana, J. 20, 21, 31

M

Makarov, I.A. 28, 42 Mamone, S. 51 Mandre, I. 27 Mann, A. 20, 21 Mansart, B. 20 Marchesoni, F. 24 Meier, S.B. 51 Mikheyenkov, A.V. 29 Murata, Y. 51

N

Nagel, U. 49, 51 Nagirnyi, V. 77 Nikolaev, S.V. 30 Nishida, T. 51

O

Odeh, A. 20 Örd, T. 46, 66, 68 Ostrovsky, S.M. 13 Ovchinnikov, S.G. 28, 30, 42, 61

P

Pae, K. 54 Palii, A.V. 13 Palm, V. 75

Patriarca, M. 24, 35 Peikolainen, A.‐L. 57 Piazza, F. 32 Pishtshev, A. 53 Potyomina, L.G. 38 Povarov, K.Yu. 49

R

Rägo, K. 46, 68 Rähn, M. 75 Ratzke, M. 26 Rebane, I. 70 Reif, J. 26 Reu, O.S. 13 Reuvekamp, P. 11 Richter, J. 43 Röhler, J. 40 Rõõm, T. 48, 49, 51 Rousochatzakis, I. 43 Rübhausen, M. 41 Rubin, P. 53, 62, 67 Russell, F.M. 12 Ryabov, D.S. 25, 37

S

Sanejouand, Y.‐H. 32 Schreiber, M. 62 Sebald, G. 58 Seibold, G. 31, 63 Shcherbinin, S. 37 Shelkan, A. 55, 59 Sherman, A. 60, 62, 64 Shneyder, E.I. 28, 42, 61 Shugai, A. 51 Silaev, M. 22 Sirutkaitis, V. 77 Sorkin, B. 76 Steinigeweg, R. 33 Stern, R. 17, 45, 65 Syassen, K. 16 Szymczak, H. 47

T

Tamm, A. 57 Tehver, I. 73 Tramontana, A. 21


81 Author index

Tsirlin, A.A. 17, 43, 65 Tsukerblat, B. 13 Turro, N.J. 51

U

Uhlig, S. 26

V

Vaikjärv, T. 71 van den Brink, J. 15 Vargunin, A. 46, 66, 68 Varlamova, O. 26 Vielhauer, S. 77 Viirok, J. 72 Voitenko, A.I. 47 Volz, S. 38

von Oelsen, E. 63

W

Whangbo, M.‐H. 16 Whitby, J. 51 Wulf, E. 49

Y

Yudson, V.I. 44

Z

Zakharov, P.V. 36 Zheludev, A. 49 Zinke, R. 43


82 Timetable

Timetable

Thursday(30.04)

Friday(01.05)

Saturday(02.05)

Sunday(02.05)

09:00 Welcome

Strongcorrelations

Ovchinnikov[O18]

Stronginteractions Yudson[O34]

09:25

Latticedynamics

Bussmann‐Holder[O01]

Mikheyenkov[O19]

Heinmaa[O35]

09:50 Russell[O02] Nikolaev[O20]

Litak[O36]

10:15 Tsukerblat[O03] Seibold[O21] Gabovich[O37]

10:40 Archilla[O04] Coffeebreak Coffeebreak

11:00 Coffeebreak

Latticedynamics

Piazza[O22]

Stronginteractions Rõõm[O38]

11:25

Strongcorrelations vandenBrink

[O05]Brenig[O23]

Hüvonen[O39]

11:50 Kremer[O06] Dubinko[O24] Karatsuba[O40]

12:15 Stern[O07] Patriarca[O25] Shugai[O41]

12:40 Büchner[O08]Lunch

Closing

13:00 Lunch

14:00

Superconductivity

Bianconi[O09]

Latticedynamics

Dmitriev[O26]

14:25 Lorenzana[O10] Shcherbinin[O27]

14:50 Mann[O11] Kosevich[O28]

15:15 Silaev[O12]

Letz[O29]

15:40 Coffeebreak Coffeebreak

16:00

Latticedynamics

Coelho[O13]

Strongcorrelations Röhler[O30]

16:25 Heinsalu[O14] Rübhausen[O31]

16:50 Chechin[O15]

Makarov[O32]

17:15 Uhlig[O16]

Tsirlin[O33]

17:40 Kalda[O17]

18:00 Postersession[P01‐26]19:00 Welcome

receptionandearlyregistration

Conferencedinner19:30

21:00

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