100y highlights 1110 hyperlinks

8/2/2019 100Y Highlights 1110 Hyperlinks

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ABSTRACTS

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iopscience.org/centenary

Celebrating 100 years ofsuperconductivity

100yearsof

supe

rconductiv

ity
http://iopscience.iop.org/centenaryhttp://iopscience.iop.org/centenary


2/16

Reasons to publish with IOP Publishing:

IOP Publishing is a leading scientific publisher that specializes in physics and related subjects. We

are an integral part of the Institute of Physics, an international learned society and professional body,

whose mission is to promote the advancement and dissemination of physics worldwide.

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Superconductor Science and Technology

EPL

Journal of Physics: Condensed Matter

Physica Scripta

New Journal of Physics


3/16

Celebrating 100 years of superconductivity

Centenial brochure 3

Dear colleagues,

On the 100th anniversary of the discovery of superconductivity, it is

interesting to ask how the field is faring after a century. After all, it was on

the fiftieth anniversary, in 1961, when Brian Pippard gave his famous The

Cat and the Cream speech to an audience at IBM, claiming that (four

years after the publication of the BCS theory) the essential fundamental

problems in low-temperature physics had been solved. All that remained,

he argued, was for the giant industrial laboratories of the day to apply

these ideas, lapping up what cream remained. If one now examinesthe list of the best superconductivity papers published by IOP journals,

one is confronted with a very different impression: hardly a dying field,

superconductivity today is driven by the continuing discoveries of new

materials.

These discoveries are still taking place in university departments as well

as governmental labs, while industrial labs have almost retired from the

scene. Papers on heavy fermions, cuprates, ruthenates, borides fullerides,

organics, MgB2

and, most recently, Fe-based materials dominate the

publications listed from the last three decades. Moreover, in almost every

case the discovery of a new class of superconductors has forced theorists

to re-examine cherished theoretical paradigms, many of which are debated

in the pages reproduced here. Indeed, Pippards speech encouraged Phil

Anderson to distill his own ideas as to why emergent quantum phenomena

like superconductivity mean more is different, and are as fundamental

to physics as elementary particles.

As the reader browses the stimulating collection of papers assembled

by the publishers, I hope he or she will take a moment to reflect upon thediversity of materials represented here, and the remarkably dynamic nature

of the superconductivity field a century after Kammerlingh Onnes original

discovery.

100yearsof

supe

rconductiv

ity

Peter Hirschfeld,

Editorial Board Member,


Image inspired by the crystal structure ofsuperconducting compounds potassiumbuckide and magnesium diboride.


4/16


4 Centen ia l b r ochu re

Journal of Physics: Condensed Matterpublishes experimental, theoretical and simulation studies that cover

all areas of condensed matter physics. Papers are published under the following sections: surface, interface

and atomic-scale science; liquids, soft matter and biological physics; nanostructures and nanoelectronics;

solid structure and lattice dynamics; electronic structure; correlated electrons; superconductors and metals;

semiconductors; dielectrics and ferroelectrics; magnetism and magnetic materials.

Authors of timely, novel work can benefit from our fast track communications (FTCs) which offer open

access with no publication charge. FTCs report exciting new developments in condensed matter physics and

are on average published online within 40 days of receipt. Superconductivity features strongly in our recent

FTCs and some of these can be viewed in our special collection which can be found via our homepage

http://iopscience.iop.org/jpcm .

Journal of Physics: Condensed Matter

iopscience.org/[email protected]

Superconductor Science and Technologyis an international multidisciplinary journal for papers on all aspects

of superconductivity. With an Impact Factor of 2.694 (2009 Thomson-Reuters ISI), it is the leading journal

specialising in superconductivity. Its coverage includes theories of superconductivity, the basic physics of

superconductors, the relation of microstructure and growth to superconducting properties, the theory of novel

devices, and the fabrication and properties of thin films and devices. It also encompasses the manufacture

and properties of conductors, and their application in the construction of magnets and heavy current

machines, together with enabling technology. More details on subject coverage can be found here:

http://iopscience.iop.org/0953-2048/page/Scope

We also offer open access to outstanding short articles, called rapid communications, reporting new and

timely developments in superconductivity and its applications. They should report very substantial new

advances in superconductivity to the readers ofSuperconductor Science and Technology, but are not

expected to meet any requirement of general interest. These articles will be processed quickly (average

receipt to online publication for rapid communications is around 60 days) and are permanently free to read

in the electronic journal.

iopscience.org/sust

[email protected]


To celebrate 100 years of superconductivity we have chosen 25 articles selected for their relevance

and impact. Their abstracts are shown here in this special collectors edition brochure.

The selected articles have been chosen from five journals: Superconductor Science and Technology,Journal of Physics: Condensed Matter, New Journal of Physics, EPL and Physica Scripta.

We hope that you will find this collection stimulating and useful throughout this centennial year of

superconductivity and beyond.

All articles can be found on our centennial websitewww.iopscience.org/centenaryand are free to

read until 31 December 2011.
http://iopscience.iop.org/centenaryhttp://iopscience.iop.org/centenary


5/16



EPL publishes original, high-quality Letters in all areas of physics, ranging from condensed matter topics and

interdisciplinary research to astrophysics, geophysics, plasma and fusion sciences, including those with

application potential. Articles must contain sufficient argument and supporting information to satisfy workers

in the field, and must also be of interest and relevance to wider sections of the physics community. Four

volumes comprising six issues each are published each year.

EPL is published under the scientific policy and control of the European Physical Society by EDP Sciences,

IOP Publishing and Societ Italiana di Fisica for a partnership of 17 European physical societies (the EPLAssociation).

www.epljournal.org

[email protected]

EPL

Physica Scripta is an international journal for experimental and theoretical physics comprising strong

components of atomic, molecular and optical physics, plasma physics, condensed matter physics and

mathematical physics. The journal also publishes Comments in five different sections and maintains a

programme of Topical Issues alongside the regular 12 issues of the main journal each year.

Physica Scripta is published by IOP Publishing on behalf of the Royal Swedish Academy of Sciences for the

Science Academies and the Physical Societies of the Nordic Countries.

[email protected]

Physica Scripta

New Journal of Physics, co-owned by the Institute of Physics and Deutsche Physikalische Gesellschaft, is an

electronic-only, open-access journal publishing original research across the whole of physics, encompassing

pure, applied, theoretical and experimental research, as well as interdisciplinary topics where physics forms

the central theme.

NJP publishes articles of outstanding scientific quality that merit the attention and interest of the whole

physics community. All content is available free to readers around the world and is funded by article

publication charges.

www.njp.org

[email protected]


ELECTRONIC

ONLY

OPEN

ACCESS


6/16



Contents

page

Superconductivity in the iron-based F-doped layered quaternary compound Nd[O1x

Fx]FeAs 8

Zhi-An Ren et al

Sr2RuO

4: an electronic analogue of3He? 8

T M Rice and M Sigrist

Near-degeneracy of several pairing channels in multiorbital models for the Fe pnictides 8S Graseret al

Superconductivity at 53.5 K in GdFeAsO1-

8Jie Yanget al

Competing orders and spin-density-wave instability in La(O1x

Fx)FeAs 9

J. Donget al

Specific heat of MgB2in a one- and a two-band model from first-principles calculations 9

A A Golubovet al

High-temperature macroscopic entanglement 9Vlatko Vedral

Crystallographic phase transition and high-Tcsuperconductivity in LaFeAsO:F 9

T Nomuraet al

Observation of Fermi-surfacedependent nodeless superconducting gaps in Ba0.6

K0.4

Fe2As

2 10

H. Dinget al

Superconductivity up to 29 K in SrFe2As

2and BaFe

2As

2at high pressures 10

Patricia L Alirezaet al

Spin susceptibility in superconductors without inversion symmetry 10P A Frigeri et al

Effect of strain, magnetic field and field angle on the critical current density of Y Ba2Cu

3O

7coated conductors 10

D C van der Laan et al

Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO1

(Re = rare-earth metal) 11without fluorine dopingZhi-An Ren et al

Pressure-induced superconductivity in CaFe2As

2 11

Tuson Park et al

Influence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, 11PrFeAsO and NdFeAsOMichael A McGuire et al

DC superconducting quantum interference devices fabricated using bicrystal grain boundary junctions in 12

Co-doped BaFe2As2 epitaxial filmsTakayoshi Katase et al
http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/1367-2630/11/2/025016/http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/1367-2630/6/1/102/http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/1367-2630/6/1/115/http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0953-8984/20/32/322204http://iopscience.iop.org/0953-8984/20/32/322204http://iopscience.iop.org/0953-8984/20/32/322204http://iopscience.iop.org/0953-8984/20/32/322204http://iopscience.iop.org/1367-2630/11/2/025011/http://iopscience.iop.org/1367-2630/11/2/025011/http://iopscience.iop.org/1367-2630/11/2/025011/http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/1367-2630/11/2/025011/http://iopscience.iop.org/0953-8984/20/32/322204http://iopscience.iop.org/0295-5075/83/1/17002http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/1367-2630/6/1/115/http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/1367-2630/6/1/102/http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/1367-2630/11/2/025016/http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0295-5075/82/5/57002


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Superconductivity at 25 K in hole-doped (La1x

Srx)OFeAs 12

Hai-Hu Wen et al

The stripe critical point for cuprates 12A Bianconiet al

Effect of 3d transition metal doping on the superconductivity in quaternary fluoroarsenide CaFeAsF 13Satoru Matsuishi et al

Superconductivity: its role, its success and its setbacks in the Large Hadron Collider of CERN 13Lucio Rossi

Thorium-dopinginduced superconductivity up to 56 K in Gd1x

ThxFeAsO 14

Cao Wanget al

The FrhlichCoulomb model of high-temperature superconductivity and charge segregation in the cuprates 14A S Alexandrov and P E Kornilovitch

Topological insulators and superconductors: tenfold way and dimensional hierarchy 15Shinsei Ryu et al

Nanoscale disorder in pure and doped MgB2thin films 15

Y Zhuet al

BCS theory of superconductivity: it is time to question its validity 15J E Hirsc
http://iopscience.iop.org/http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0953-8984/12/50/326http://iopscience.iop.org/1367-2630/11/2/025012/http://iopscience.iop.org/0953-2048/23/3/034001http://iopscience.iop.org/0295-5075/83/6/67006http://iopscience.iop.org/0295-5075/83/6/67006http://iopscience.iop.org/0295-5075/83/6/67006http://iopscience.iop.org/0295-5075/83/6/67006http://iopscience.iop.org/0295-5075/83/6/67006http://iopscience.iop.org/0953-8984/14/21/308http://iopscience.iop.org/1367-2630/12/6/065010/http://iopscience.iop.org/0953-2048/23/9/095008http://iopscience.iop.org/0953-2048/23/9/095008http://iopscience.iop.org/0953-2048/23/9/095008http://iopscience.iop.org/1402-4896/80/3/035702http://iopscience.iop.org/1402-4896/80/3/035702http://iopscience.iop.org/0953-2048/23/9/095008http://iopscience.iop.org/1367-2630/12/6/065010/http://iopscience.iop.org/0953-8984/14/21/308http://iopscience.iop.org/0295-5075/83/6/67006http://iopscience.iop.org/0953-2048/23/3/034001http://iopscience.iop.org/1367-2630/11/2/025012/http://iopscience.iop.org/0953-8984/12/50/326http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/


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Superconductivity in the iron-based F-doped

layered quaternary compound Nd[O1x

Fx]

FeAs

Z Ren, J Yang, W Lu, W Yi, X Shen et al

2008 EPL 8257002

Abstract

Here we report a new quaternary iron-arsenide superconductor Nd[O1x

Fx]

FeAs, with the onset resistivity transition at 51.9 K and Meissner transition

at 51 K. This compound has the same crystal structure as LaOFeAs,

and becomes the second superconductor after Pr[O1x

Fx]FeAs that

superconducts above 50 K.

Near-degeneracy of several pairing channels

in multiorbital models for the Fe pnictidesS Graser, T A Maier, P J Hirschfeld and D J Scalapino

2009 New J. Phys. 11025016

Abstract

Weak-coupling approaches to the pairing problem in the iron pnictide

superconductors have predicted a wide variety of superconducting ground

states. We argue here that this is due both to the inadequacy of certain

approximations to the effective low-energy band structure, and to the

natural near degeneracy of different pairing channels in superconductors

with many distinct Fermi surface sheets. In particular, we review attempts

to construct two-orbital effective band models, the argument for their

fundamental inconsistency with the symmetry of these materials, and

compare the dynamical susceptibilities of two- and five-orbital tight-binding

models. We then present results for the magnetic properties, pairing

interactions and pairing instabilities within a five-orbital tight-bindingrandom phase approximation model. We discuss the robustness of

these results for different dopings, interaction strengths and variations in

band structures. Within

the parameter space

explored, an anisotropic,

sign-changing s-wave (A1g

)

state and a dx2y2

(B1g

) state

are nearly degenerate, due

to the near nesting of Fermi

surface sheets.

Superconductivity at 53.5 K in GdFeAsO1-

J Yang, Z Li, W Lu, W Yi, X Shen, Z Ren, G Che, X Dong, L Sunet al

2008 Supercond. Sci. Technol.21 082001

AbstractHere we report the fabrication and superconductivity of the iron-based

arsenic oxide GdFeAsO1

compound with oxygen-deficiency, which has

an onset resistivity transition temperature at 53.5 K. This material has the

same crystal structure as the newly discovered high-TcReFeAsO

1family

(Re = rare earth metal) and a further reduced crystal lattice, while the Tc

starts to decrease compared with the SmFeAsO1

system.

Sr2RuO

4: an electronic analogue of3He?

T M Rice and M Sigrist

1995J. Phys.: Condens. Matter7 L643

Abstract

Sr2RuO4 is a superconductor with a similar structure to a high-Tc cupratesuperconductor. Nevertheless, the superconducting state may have

different symmetry than that of cuprate superconductors. Strong Hunds

rule coupling favours triplet over singlet pairing, similar to 3He. A strong

candidate is the odd-parity pairing state which is the two-dimensional

analogue of the BalianWerthamer state of3He. Various experimental

consequences and tests are analysed.

Figure 2: The temperature dependence of resistivity for the Nd[O0.89

F0.11

]FeAs superconductor.

Figure 1: The crystal structure ofLaOFeAs showing the FeAs layers

with an Fe square lattice (red) and

As atoms (yellow) in a pyramidal

configuration above and below the

Fe plane.

For full-text downloads of the 25 selected articles, plus

articles on iron-based superconductors and by Nobel PrizeLaureates, please visitiopscience.org/centenary

100yearsof

sup

erconduc

tivit

y
http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/1367-2630/11/2/025016/http://iopscience.iop.org/1367-2630/11/2/025016/http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/centenaryhttp://iopscience.iop.org/0953-2048/21/8/082001http://iopscience.iop.org/1367-2630/11/2/025016/http://iopscience.iop.org/0953-8984/7/47/002http://iopscience.iop.org/0295-5075/82/5/57002http://iopscience.iop.org/centenary


9/16



Competing orders and spin-density-wave

instability in La(O1x

Fx)FeAs

J. Dong, H. J. Zhang, G. Xu, Z. Li, G. Li, W. Z. Hu, D. Wu, G. F. Chen, X. Dai,

J. L. Luo, Z. Fang and N. L. Wang

2008 EPL83 27006

Abstract

The interplay between different ordered phases, such as superconducting,

charge or spin ordered phases, is of central interest in condensed-matter

physics. The very recent discovery of superconductivity with a remarkable

Tc=26 K in Fe-based oxypnictide La(O

1xFx)FeAs (see Kamihara Y. et al.,

J. Am. Chem. Soc.,130 (2008) 3296) is a surprise to the scientific

community and has generated tremendous interest. The pure LaOFeAs itself

is not superconducting but shows an anomaly near 150 K in both resistivity

and dc magnetic susceptibility. Here we provide combined experimental

and theoretical evidences showing that a spin-density-wave (SDW) state

develops at low temperature, in association with electron Nematic order.The electron-doping by F suppresses the SDW instability and induces the

superconductivity. Therefore, the La(O1x

Fx)FeAs offers an exciting new

system showing competing orders in layered compounds.

Specific heat of MgB2in a one- and a two-

band model from first-principles calculationsA A Golubov, J Kortus, O V Dolgov, O Jepsen, Y Kong, O K Andersen, B J Gibson,

K Ahn and R K Kremer

2002J. Phys.: Condens. Matter14 1353

Abstract

The heat capacity anomaly at the transition to superconductivity of the

layered superconductor MgB2is compared to first-principles calculations

with the Coulomb repulsion, *, as the only parameter which is fixed to give

the measured Tc. We solve the Eliashberg equations for both an isotropic

one-band model and a two-band model with different superconducting

gaps on the -band and-band Fermi surfaces. The agreement with

experiments is considerably better

for the two-band model than for the

one-band model.

Figure 3: Experimental data on the

heat capacity difference. The dashed

curve is the theoretical result from the

one-band model and the thick solid curve

corresponds to the two-band model, from

the solution of the Eliashberg equations.

shown to be equivalent to calculating multipartite entanglement in totally

symmetric states of qubits. It is demonstrated that we can conclusively

calculate the relative entropy of entanglement within any subset of qubits

in the overall symmetric state. Three main results are then presented. First,

the condition for superconductivity, namely existence of the off-diagonal

long-range order (ODLRO), is dependent not on two-site entanglement

but just classical correlations as the sites become more and more distant.

Secondly, the entanglement that does survive in the thermodynamical

limit is the entanglement of the total lattice and, at half-filling, it scales

with the log of the number of sites. It is this entanglement that will exist at

temperatures below the superconducting critical temperature, which can

currently be as high as 160 K. Finally, it is proved that a complete mixture

of symmetric states does not contain any entanglement in the macroscopic

limit. On the other hand, a mixture of symmetric states possesses the

same two qubit entanglement features as the pure states involved, in the

sense that the mixing does not destroy entanglement for a finite number of

qubits, albeit it does decrease it. Furthermore, maximal mixing of symmetric

states does not destroy ODLRO and classical correlations. We discuss

generalizations to the subsystems of any dimensionality (i.e. higher than

spin-half).

High-temperature macroscopic entanglementVlatko Vedral

2004 New J. Phys. 6102

AbstractIn this paper, we intend to show that macroscopic entanglement is possible

at high temperatures. We have analysed multipartite entanglement

produced by the-pairing mechanism, which features strongly in the

fermionic lattice models of high Tcsuperconductivity. This problem is

Crystallographic phase transition and high-Tc

superconductivity in LaFeAsO:FT Nomura, S W Kim, Y Kamihara, M Hirano, P V Sushko, K Kato, M Takata,

A L Shluger, and H Hosono

2008 Supercond. Sci. Technol. 21125028

Abstract

Undoped LaFeAsO, the parent compound of the newly found high-Tcsuperconductor, exhibits a sharp decrease in the temperature-dependent

resistivity at~160 K. The anomaly can be suppressed by F doping with

simultaneous appearance of superconductivity appears correspondingly,

suggesting a close association of the anomaly with the superconductivity.

We examined the crystal structures, magnetic properties and conductivity

of undoped (normal conductor) and 14 at.% F-doped LaFeAsO (Tc= 20 K)

by synchrotron x-ray diffraction (XRD), DC magnetic measurements, and

ab initio calculations demonstrated that the anomaly is associated with

a phase transition from tetragonal (P4/nmm) to orthorhombic (Cmma)

phases at~160 K as well as an antiferromagnetic spin ordering transition

at~140 K. These transitions can be explained by spin configuration-

dependent potential energy surfaces derived from the ab initio calculations.

The suppression of the transitions is ascribed to interrelated effects of

geometric and electronic structural changes due to doping by F ions.

Figure 1: Crystal structure of LaFeAsO. (a) Schematic view of the crystal structure, demonstratingthe layered structure. (b) Top view of the crystal structure from the c-direction.
http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0295-5075/83/2/27006http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/1367-2630/6/1/102/http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/0953-2048/21/12/125028http://iopscience.iop.org/1367-2630/6/1/102/http://iopscience.iop.org/0953-8984/14/6/320http://iopscience.iop.org/0295-5075/83/2/27006


10/16


10 Centenial brochure

Observation of Fermi-surfacedependent

nodeless superconducting gaps in

Ba0.6

K0.4

Fe2As

2

H. Ding, P. Richard, K. Nakayama, K. Sugawara, T. Arakane, Y. Sekiba,A. Takayama, S. Soumaet al

2008 EPL83 47001

Abstract

We have performed a high-resolution angle-resolved photoelectron

spectroscopy study on the newly discovered superconductor Ba0.6

K0.4

Fe2As

2

(Tc=37 K). We have observed two superconducting gaps with different

values: a large gap (~12 meV) on the two small hole-like and electron-like

Fermi surface (FS) sheets, and a small gap (~6 meV) on the large hole-like

FS. Both gaps, closing simultaneously at the bulk transition temperature

(Tc), are nodeless and nearly isotropic around their respective FS sheets.

The isotropic pairing interactions are strongly orbital dependent, as the

ratio 2/kBTc switches from weak to strong coupling on different bands.The same and surprisingly large superconducting gap due to strong pairing

on the two small FSs, which are connected by the (, 0) spin-density-

wave vector in the parent compound, strongly suggests that the pairing

mechanism originates from the inter-band interactions between these two

nested FS sheets.

Figure 4:The superconducting transition temperature and superconducting volume fraction of

AFe2As

2(ASr, Ba) as a function of pressure.

Figure 2: Finite element analysis-calculated strain profile of the bending spring for the two

bending directions

Superconductivity up to 29 K in SrFe2As

2

and BaFe2As

2at high pressures

P Alireza, Y T Chris Ko, J Gil lett, C Petrone, J Cole, G Lonzarich and S Sebastian


Abstract

We report the discovery of superconductivity at high pressure in SrFe2As

2

and BaFe2As

2. The superconducting transition temperatures are up to 27 K

in SrFe2As

2and 29 K in BaFe

2As

2, the highest obtained for materials with

pressure-induced superconductivity thus far.

Effect of strain, magnetic field and field angle

on the critical current density of Y Ba2Cu

3O

7

coated conductorsD C van der Laan, J W Ekin, J F Douglas, C C Clickner, T C Stauffer and

L F Goodrich


Abstract

A large, magnetic-field-dependent, reversible reduction in critical current

density with axial strain in Y Ba2Cu

3O

7coated conductors at 75.9 K

has been measured. This effect may have important implications for the

performance of Y Ba2Cu

3O

7coated conductors in applications where

the conductor experiences large stresses in the presence of a magnetic

field. Previous studies have been performed only under tensile strain and

could provide only a limited understanding of the in-field strain effect.

We now have constructed a device for measuring the critical current

density as a function of axial compressive and tensile strain and applied

magnetic field as well as magnetic field angle, in order to determine the

magnitude of this effect and to create a better understanding of its origin.

The reversible reduction in critical current density with strain becomes larger

with increasing magnetic field at all field angles. At 76 K the critical current

density is reduced by about 30% at 0.5% strain when a magnetic field of5 T is applied parallel to the c-axis of the conductor or 8 T is applied in the

ab-plane, compared to a reduction of only 13% in self-field. Differences

in the strain response of the critical current density at various magnetic

field angles indicate that the pinning mechanisms in Y Ba2Cu

3O

7coated

conductors are uniquely affected by strain.

Spin susceptibility in superconductors

without inversion symmetryP A Frigeri, D F Agterberg and M Sigrist

2004 New J. Phys.6 115

Abstract

In materials without spatial inversion symmetry, the spin degeneracy of

the conduction electrons can be lifted by an antisymmetric spinorbit

coupling. We discuss the influence of this spinorbit coupling on the spin

susceptibility of such superconductors, with a particular emphasis on the

recently discovered heavy Fermion superconductor CePt3Si. We find that,

for this compound (with tetragonal crystal symmetry) irrespective of the

pairing symmetry, the stable superconducting phases would give a very

weak change of the spin susceptibility for fields along the c-axis and an

intermediate reduction for fields in the basal plane. We also comment on

the consequences for the paramagnetic limiting in this material.
http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0295-5075/83/4/47001http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/1367-2630/6/1/115/http://iopscience.iop.org/1367-2630/6/1/115/http://iopscience.iop.org/0953-2048/23/7/072001http://iopscience.iop.org/1367-2630/6/1/115/http://iopscience.iop.org/0953-8984/21/1/012208http://iopscience.iop.org/0295-5075/83/4/47001


11/16


Centen ia l b r ochu re 11

Superconductivity and phase diagram in

iron-based arsenic-oxides ReFeAsO1

(Re = rare-earth metal) without fluorine doping

Z Ren, G Che, X Dong, J Yang, W Lu, W Yi, X Shen, Z Li, L Sun, F Zhou and Z Zhao

2008 EPL 8317002

Abstract

Here we report a new class of superconductors prepared by high-pressure

synthesis in the quaternary family ReFeAsO1

(Re=Sm, Nd, Pr, Ce, La)

without fluorine doping. The onset superconducting critical temperature (Tc)

in these compounds increases with the reduction of the Re atom size, and

the highestTcobtained so

far is 55 K in SmFeAsO1

.

For the NdFeAsO1

compound with different

oxygen concentration

a dome-shaped phase

diagram was found.

Pressure-induced superconductivity in

CaFe2As

2

T Park, E Park, H Lee, T Klimczuk, E D Bauer, F Ronning and J D Thompson


Abstract

We report pressure-induced superconductivity in a single crystal of

CaFe2As

2. At atmospheric pressure, this material is antiferromagnetic

below 170 K but under an applied pressure of 0.69 GPa becomes

superconducting, with a transition temperature Tcexceeding 10 K. The

rate ofTcsuppression with applied magnetic field is 0.7 K T1, giving an

extrapolated zero-temperature upper critical field of 1014 T.

Figure 2:The temperature

dependences of resistivity for the

nominal ReFeAsO0.85

samples

synthesized by the HP method.

Figure 1: Temperature dependence of the normalized resistance of CaFe2As

2. Resistance divided

by its room-temperature value is plotted against temperature for 1 bar (squares) and 0.69 GPa

(circles).

Influence of the rare-earth element on

the effects of the structural and magnetic

phase transitions in CeFeAsO, PrFeAsO and

NdFeAsOM McGuire, R Hermann, A Sefat, B Sales, R Jin, D Mandrus, F Grandjean

and G Long

2009 New J. Phys. 11025011

Abstract

We present results of transport and magnetic properties and heat capacity

measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These

materials undergo structural phase transitions, spin density wave-like

magnetic ordering of small moments on iron and antiferromagnetic ordering

of rare-earth moments. The temperature dependence of the electrical

resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient and

magnetoresistance are reported. The magnetic behavior of the materialshave been investigated using Mssbauer spectroscopy and magnetization

measurements. Transport and magnetic properties are affected strongly

by the structural and magnetic transitions, suggesting significant changes

in the band structure and/or carrier mobilities occur, and phononphonon

scattering is reduced upon transformation to the low-temperature structure.

Results are compared with recent reports for LaFeAsO, and systematic

variations in properties as the identity of Ln is changed are observed

and discussed. As Ln progresses across the rare-earth series from La to

Nd, an increase in the hole contributions to the Seebeck coefficient and

increases in magnetoresistance and the Hall coefficient are observed in

the low-temperature phase. Analysis of hyperfine fields at the iron nuclei

determined from Mssbauer

spectra indicates that

the moment on Fe in the

orthorhombic phase is nearly

independent of the identity

of Ln, in apparent contrast

to reports of powder neutron

diffraction refinements.

Figure 5: The lattice thermal conduc-

tivityLof CeFeAsO, PrFeAsO and

NdFeAsO. Results for LaFeAsO are

included for comparison.

Download all the full-text articleswithin this brochure at:

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12/16



Figure 3: Voltageflux (V) characteristics of the dc-SQUID made using BaFe2As

2:Co epitaxial

film on a (La, Sr)(Al, Ta)O3bicrystal substrate bicrystal substrate measured at 14 K.

Figure 2: The temperature

dependence of resistivity of

samples (La1x

Srx)OFeAs

with the Sr concentrationx

changing from 0.10 to 0.20.

One can see that the onset

transition temperatures

marked here by arrows are

quite close to each other, with

the highestTc 25.6K at

the doping of 0.13. Beyond

x0.20, no superconductiv-

ity was observed.

DC superconducting quantum interference

devices fabricated using bicrystal grain

boundary junctions in Co-doped BaFe2As

2

epitaxial filmsT Katase, Y Ishimaru, A Tsukamoto, H Hiramatsu, T Kamiya, K Tanabe

and H Hosono


Abstract

DC superconducting quantum interference devices (dc-SQUIDs) were

fabricated in Co-doped BaFe2As

2epitaxial films on (La, Sr)(Al, Ta)O

3

bicrystal substrates with 30 misorientation angles. The 18 8 m2 SQUID

loop with an estimated inductance of 13 pH contained two 3 m wide

grain boundary junctions. The voltageflux characteristics clearly exhibited

periodic modulations with V= 1.4 V at 14 K, while the intrinsic flux noise

of dc-SQUIDs was 7.8 105

0 Hz1/2

above 20 Hz. The rather high fluxnoise is mainly attributed to the small voltage modulation depth which

results from the superconductornormal-metalsuperconductor junction

nature of the bicrystal grain boundary.

Superconductivity at 25 K in hole-doped

(La1x

Srx)OFeAs

H Wen, G Mu, L Fang, H Yang and X Zhu

2008 EPL82 17009

Abstract

By partially substituting the tri-valence element La with di-valence element

Sr in LaOFeAs, we introduced holes into the system. For the first time, we

successfully synthesized the hole-doped new superconductors

(La1x

Srx)OFeAs. The maximum superconducting transition temperature

at about 25 K was observed at a doping level ofx0.13. It is evidenced

by Hall effect measurements that the conduction in this type of material

is dominated by hole-like charge carriers, rather than electron-like ones.

Together with the data of the electron-doped system La(O1x

Fx)FeAs, a

generic phase diagram is depicted and is revealed to be similar to that of

the cuprate superconductors.

Papers by Nobel Laureates

Magneto oscillations in unconventional superconductorswell below Hc2J R Schrieffer2002 Physica Scripta

High-temperature superconductivitydream or reality?Vitalii L Ginzburg1976 Soviet Physics Uspekhi

Effect of high pressure on the superconductingproperties of metals N B Brandt and N I Ginzburg1965

Soviet Physics Uspekhi

Mixed order parameter symmetries in cuprate

superconductorsA Bussmann-Holderet al2007 EPL(Europhysics Letters)

The search for new high temperature superconductorsK A Mller2006 Superconductor Science and

Technology

Superconductivity due to ferromagnetically orderedlocalized spinsA A Abrikosov2001Journal of Physics:

Condensed Matter

Depinning of charge-density-waves by quantumtunnelingJohn Bardeen 1989 Physica Scripta
http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0953-2048/23/8/082001http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0295-5075/82/1/17009http://iopscience.iop.org/0953-2048/23/8/082001


13/16



The stripe critical point for cupratesA Bianconi, G Bianconi, S Caprara, D Di Castro, H Oyanagi and N L Saini

2000J. Phys.: Condens. Matter1210655

Abstract

The experimental determination of the quantum critical point (QCP)

that triggers the self-organization of charged striped domains in

cuprate perovskites is reported. The phase diagram of doped cuprate

superconductors is determined by a first variable, the hole doping, and a

second variable, the micro-strain of the Cu-O bond length, obtained from

the Cu K-edge extended x-ray absorption fine structure. For a fixed optimum

doping,c= 0.16, we show the presence of the QCP for the onset of local

lattice distortions and stripe formation at the critical micro-strain c. The

critical temperature Tc(,) reaches its maximum at the quantum critical

point (c,

c) for the formation of bubbles of superconducting stripes. The

critical charge, orbital and spin fluctuations near this strain QCP provide the

interaction for the pairing.

Figure 6: The superconducting critical temperature Tcplotted as a colour plot (from T

c 0 K,

black, to Tc135 K, through yellow to white) as a function of the micro-strain and doping.

Effect of 3d transition metal doping on

the superconductivity in quaternary

fluoroarsenide CaFeAsFSatoru Matsuishi, Yasunori Inoue, Takatoshi Nomura, Youichi Kamihara,

Masahiro Hirano and Hideo Hosono

2009 New J. Phys.11 025012

Abstract

We examined the doping effect of 3d transition metal (TM) elements (Cr,

Mn, Co, Ni and Cu) at the Fe site of a quaternary fluoroarsenide CaFeAsF,

an analogue of 1111-type parent compound LaFeAsO. The anomaly at

~120 K observed in resistivity () versus temperature (T) plot for the parent

compound is suppressed by the doping of each TM element. Furthermore,

Co and Ni doping (CaFe1x

TMxAsF, TM = Co,Ni) induces superconductivity

with a transition temperature maximized at the nominalx= 0.10 for Co

(22 K) and atx= 0.05 for Ni (12 K). These optimal doping levels may be

understood by considering that Ni2+(3d8) adds double electrons to the

FeAs layers compared with Co2+ (3d7). Increasedxfor Co or Ni breaksthe superconductivity, while metallic nature d/dT> 0 is still kept. These

observations indicate that Co and Ni serve as electron donors. In contrast,

Cr, Mn and Cu doping does not induce superconductivity, yielding

d/dT< 0 below the T anomaly temperature, indicating that these TM

ions act as scattering centers. The two different types of behavior of TM

replacing the Fe site are discussed in relation to the changes in the lattice

constants with doping.

Superconductivity: its role, its success and

its setbacks in the Large Hadron Collider of

CERNLucio Rossi


Abstract

The Large Hadron Collider (LHC), the particle accelerator at CERN, Geneva,

is the largest and probably the most complex scientific instrument ever

built. Superconductivity plays a key role because the accelerator is based

on the reliable operation of almost 10 000 superconducting magnetscooled by 130 tonnes of helium at 1.9 and 4.2 K and containing a total

stored magnetic energy of about 15 000 MJ (including detector magnets).

The characteristics of the 1200 tonnes of high quality NbTi cables have

met the severe requests in terms of critical currents, magnetization and

inter-strand resistance; the magnets are built with an unprecedented

uniformity, about 0.01% of variation in field quality among the 1232 main

dipoles, which are 15 m in length and 30 tonnes in weight. The results of

this 20-year-long enterprise will be discussed together with problems faced

during construction and commissioning and their remedies. Particular

reference is made to the severe incident which occurred nine days after the

spectacular start-up of the machine on 10 September 2008. The status of

repair and the plan for the physics programme in 2010 are also presented.

Figure 1: The superconducting magnets in the LHC tunnel.

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14/16



Thorium-dopinginduced superconductivity

up to 56 K in Gd1x

ThxFeAsO

C Wang, L Li, S Chi, Z Zhu, Z Ren, Y Li, Y Wang, X Lin, Y Luo et al

2008 EPL83 67006

Abstract

We report a new strategy to induce superconductivity in iron-based

oxyarsenide. Instead of F substitution for O2, we employed Th4+ doping in

GdFeAsO with the consideration of lattice match between Gd2O

2layers

and Fe2As

2ones. As a result, superconductivity with T

c

onsetas high as 56 K

was realized in a Gd0.8Th

0.2FeAsO polycrystalline sample. This T

cvalue is

among the highest ever discovered in the iron-based oxypnictides.

The FrhlichCoulomb model of

high-temperature superconductivity and

charge segregation in the cupratesA S Alexandrov and P E Kornilovitch


Abstract

We introduce a generic FrhlichCoulomb model of the oxides, which

also includes infinite on-site (Hubbard) repulsion, and describe a simple

analytical method of solving the multi-polaron problem in complex lattice

structures. Two particular lattices, a zigzag ladder and a perovskite layer,

are studied. We find that, depending on the relative strength of the Frhlich

and Coulomb interactions, these systems are either polaronic Fermi (or

Luttinger) liquids, bipolaronic superconductors, or charge-segregated

insulators. In the superconducting phase the carriers are superlight

mobile bipolarons. The model describes key features of the cuprates such

as theirTc-values, the isotope effects, the normal-state diamagnetism,

the pseudogap, and spectral

functions measured in tunnelling and

photoemission. We argue that a low

Fermi energy and strong coupling of

carriers with high-frequency phonons is

the cause of high critical temperatures innovel superconductors.

Figure 1: Crystal chemistry understanding of the structure of LnFeAsO (Ln =lanthanides). The

stacking of fluorite (CaF2) layers, CsCl-type layers and antifluorite (Li

2O) layers along the c-axis

forms the LnFeAsO structure. The lattice constant along the stacking direction can be expressed

by the formula c12 aCaF2

12aCsCl

12aLi

2O, which basically satisfies the experimental results.

Note that the lattice match between the Ln2O

2layers and the Fe

2As

2layers affects the chemical

stability of LnFeAsO.

Figure 4: Four degenerate bipolaron configurations

A, B, C, and D. Some single-polaron hoppings are

indicated by arrows.

Topological insulators and superconductors:

tenfold way and dimensional hierarchyS Ryu, A Schnyder, A Furusaki and A W W Ludwig

2010 New J. Phys. 12065010

Abstract

It has recently been shown that in every spatial dimension there exist

precisely five distinct classes of topological insulators or superconductors.

Within a given class, the different topological sectors can be distinguished,

depending on the case, by a Z or a Z2topological invariant. This is an

exhaustive classification. Here we construct representatives of topological

insulators and superconductors for all five classes and in arbitrary spatial

dimension d, in terms of Dirac Hamiltonians. Using these representatives

we demonstrate how topological insulators (superconductors) in different

dimensions and different classes can be related via dimensional reduction

by compactifying one or more spatial dimensions (in KaluzaKlein-like

fashion). For Z-topological insulators (superconductors) this proceedsby descending by one dimension at a time into a different class. The

Z2-topological insulators (superconductors), on the other hand, are shown

to be lower-dimensional descendants of parent Z-topological insulators

in the same class, from which they inherit their topological properties. The

eightfold periodicity in dimension d that exists for topological insulators

(superconductors) with Hamiltonians satisfying at least one reality

condition (arising from time-reversal or charge-conjugation/particle

hole symmetries) is a reflection of the eightfold periodicity of the spinor

representations of the orthogonal groups SO(N) (a form of Bott periodicity).

Furthermore, we derive for general spatial dimensions a relation between

the topological invariant that characterizes topological insulators and

superconductors with chiral symmetry (i.e., the winding number) and the

ChernSimons invariant. For lower-dimensional cases, this formula relates

the winding number to the electric polarization (d=1 spatial dimensions)or to the magnetoelectric polarizability (d=3 spatial dimensions). Finally,

we also discuss topological field theories describing the spacetime theory

of linear responses in topological insulators (superconductors) and study

how the presence of inversion symmetry modifies the classification of

topological insulators (superconductors).

Figure 3: 2D energy spectrum of the surface states of model from Turner, Zang, and Vishwanth

(arXiv:0909.3119) with mass m50.5. There are two inequivalent surface modes in agree-

ment with the winding numberv3(m

50.5)2.
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15/16



Nanoscale disorder in pure and doped MgB2

thin filmsY Zhu, A V Pogrebnyakov, R Wilke, K Chen, X X Xi, J M Redwing, C G Zhuanget al

2010 Supercond. Sci. Technol. 23095008

Abstract

MgB2thin films have superior superconducting properties compared to bulk

MgB2and demonstrate the potential for further improving the performances

of MgB2wires and tapes. Using transmission electron microscopy, we have

characterized the microstructure of pure and C-doped MgB2using various

carbon sources grown by hybrid physicalchemical vapor deposition

(HPCVD), and cold-grownannealed film deposited by molecular beam

epitaxy (MBE). The MgB2HPCVD films increase in crystal quality in the

order (MeCp)2Mg-sourced films, CH

4-sourced films, B(CH

3)

3-sourced films,

pure films, while the Hc2 values of these films follow the opposite order.

The cold-grownannealed MgB2MBE film contains non-epitaxial 10 nm

MgB2 grains and MgO nanoparticles. The microstructural origins of electronscattering and flux pinning in both films are discussed. We also show the

structure and chemistry of the degraded phase in HPCVD films and its

effects on superconducting properties.

BCS theory of superconductivity: it is time to

question its validityJ E Hirsch

2009 Phys. Scr. 80035702

Abstract

The time-tested BardeenCooperSchrieffer (BCS) theory of

superconductivity is generally accepted to be the correct theory of

conventional superconductivity by physicists and, by extension, by

the world at large. There are, however, an increasing number of red

flags that strongly suggest the possibility that BCS theory may be

fundamentally flawed. An ever-growing number of superconductors are

being classified as unconventional, not described by the conventional

BCS theory and each requiring a different physical mechanism. In

addition, I argue that BCS theory is unable to explain the Meissner effect,

the most fundamental property of superconductors. There are several

other phenomena in superconductors for which BCS theory provides no

explanation. Furthermore, BCS theory has proven unable to predict any

new superconducting compounds. This paper suggests the possibility that

BCS theory itself as the theory of conventional superconductivity may

require a fundamental overhaul. I outline an alternative to conventional BCStheory proposed to apply to all superconductors, conventional as well as

unconventional, that offers an explanation for the Meissner effect as well

as for other puzzles and provides clear guidelines in the search for new high

temperature superconductors.

Figure 8: Bright field transmission electron microscopic images taken at the [0001] zone-axis

from the same area of (a) the as-grown and (b) the degraded pure MgB2film.

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