LCLS 10 Year – Materials ScienceApril 10, 2019Zhi-xun ShenStanford Institute for Materials and Energy SciencesStanford University and SLAC National Accelerator Laboratory

1

Material as a Driver for Scientific Discovery

Cuprate Superconductivity

Quantum Hall LiquidGiant Magnetoresistance

Graphene

Material as a platform to test concepts

D-wave Superconductivity Topological Insulators

(Limits of Schrodinger’s Equation)

Discoveries at BES light sources

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948.

Material as a driver for technology

Triumph of Quantum Theory of Solids

5

Silicon Class Materials

Some properties can already be understood … e.g., mechanical property, semiconductor behavior

Well Developed Theoretical Framework

6

• Can we develop a theoretical framework for these materials?• Discovery and synthesis of

materials platforms• Theoretical investigation and

modeling• Precision measurements to test

theory and ideas• Sophisticated understanding and

control of materials

High-temperature superconductors – e.g. beyond silicon class materials

Materials with amazing properties, silicon class theory fails

7

Why so hard? – multiple degrees of freedom and complex orders

charge density wave

spin density wave

orbital order

Jahn-Teller distortion

Emerging Properties from Coupled Interactions

Challenge to establish a predictive theoretical framework

Use Cases of LCLS

Time-resolved resonant/non-resonant x-ray diffraction at LCLS

• State of matter not exist otherwise (“driven state”)

• Experimental environment not available otherwise

• Precision measurements not achievable otherwise

pump

X-ray probeTim

e

Lattice Displacement

Diffr

actio

n

Coherent Control of Electromagnons

• X-ray scattering signal, from magnetic spiral excited state, follows the THz pulse field distribution with half-cycle delay

• Inverting the THz polarization inverts the effect, implying that the E-field drives the spiral alignment

• Effect is seen in the low-temperature, multi-ferroic state but not in the paraelectric/ spin-density wave (SDW) phase (27K < T < 42K)

T. Kubacka et al., "Large-Amplitude Spin Dynamics Driven by a THz Pulse in Resonance with an Electromagnon", Science, 343, 1333 (2014).

State of Matter does not exist otherwise

The transient structure of a better superconductorScientific Achievement

Femtosecond x-ray diffraction at the LCLS free electron laser revealed the transient crystal structure of a high-TC cuprate driven into a superconducting state above the critical temperature by light.

Significance and Impact

Knowledge of the non-equilibrium crystal structure may guide the design of materials with new functional properties, including superconductors with increased critical temperature.

Nonlinear lattice excitation in YBCO above the critical temperature causes a simultaneous increase and decrease in the Cu–O2 intra-bilayer and inter-bilayer distances, respectively, probably inducing coherent transport between the bi-layers.

R. Mankowsky, A. Subedi, M. Först, S. O. Mariager, M. Chollet, H. T. Lemke, J. S. Robinson, J. M. Glownia, M. P. Minitti, A. Frano, M. Fechner, N. A. Spaldin, T. Loew, B. Keimer, A. Georges & A. CavalleriNature 516, 71 (2014).

State of Matter does not exist otherwise

Ultrafast tuning of interlayer interactions in quasi-two-dimensional materials

Scientific Achievement Demonstration of a new method for non-equilibrium tuning of van der Waals interactions in layered materials using light pulses.

Significance and ImpactThis work shows how the the functional properties of 2D layered materials can be engineered on ultrafast time-scales via manipulation of interlayer bonding.

dichalcogenides.

Top: Schematic of experiment.Bottom: Snapshots of diffracted x-ray spot as a function of time,

probing changes in the interlayer spacing of single domain MoS2. Vertical axis is the x-ray momentum transfer.

E. Mannebach et al., “Dynamic Optical Tuning of Interlayer Interactions in the Transition Metal Dichalcogenides”, Nano Letters (2017)

State of Matter does not exist otherwise

Unveiling a Puzzling Phase in High-Tc Cuprate at High Magnetic Field

S. Gerber et al. "Three-dimensional charge density wave order in YBa2Cu3O6.67 at high magnetic fields", Science, 350, 949 (2015).

Scientific Achievement • Revealed the structure of the long-sought field-

induced charge density wave (CDW) phase in a high-Tc cuprate YBa2Cu3O6.67

• X-ray scattering with high magnetic field(28 Tesla) at LCLS

• Field-induced CDW becomes increasingly three-dimensionally ordered along with the suppression of superconductivity by magnetic field

Significance and Impact• New insight to quantum materials in presence of

high magnetic fields• Transient X-ray scattering is a powerful approach

to disentangle competing quantum phases

Experimental Environment does not exist otherwise

Ultrafast disordering of vanadium dimers in photoexcited VO2

Scientific AchievementSLAC’s x-ray laser revealed an unexpected transition through a state of disorder in the lattice of VO2 as the material transforms.

Significance and ImpactThis finding is important for the design of quantum materials with applications in sensors, smart windows, energy storage and conversion and super-efficient electrical conductors.

Upper: Snapshots of the diffuse intensity taken at LCLS. Lower: The patterns capture large regions of momentum and show an

increase in the diffuse intensity at the same time as a decrease of the superstructure Bragg peaks.

S. Wall et al., Science 362, 572–576 (2018).

Experimental Environment does not exist otherwise

14Nature Materials 8, 630 - 633 (2009)

0.30

1.00.80.60.4

Δz

Se (

pm

)

Δt (ps)

0.15

0.0016

12

8

ΔE

1 (me

V)

0.54 mJ/cm2

0.46 mJ/cm2

1.0

0.5

0.0

Δz

Se (

pm

)

1.51.00.50.0

Fluence F (mJ/cm2)

ΔzSe/Δ

F = 0

.538

(7) p

m/(m

J/cm

2 ) 8

4

00.60.40.20.0

Band 1Band 2

ΔE

(m

eV

)

F (mJ/cm2)

ΔE2/Δ

F = 1

6.2(

2.1)

meV

/(mJ/cm

2 )

ΔE 1/ΔF = 10.4(1.4)

meV/(mJ/cm

2 )

5544 mmJJ//cm222

2.0

A

D

B

C

Se

Fe

ΔzSe

ΔE1

Band 1d

xzd

yz

Y. Mizuguchi et al. Supercond Sci Tech 2010.Pressure dependence of Superconductivity in FeSe

Electron-Phonon Coupling in a Correlated Material – FeSe Case Study

Precision measurement not achievable otherwise

Quantifying electron-phonon coupling in time domain – “THz Lock In”

dE dzCombine

!"/!$

0.30

1.00.80.60.4

Δz S

e (

pm

)

Δt (ps)

0.15

0.0016

12

8

ΔE

1 (meV

)

0.54 mJ/cm2

0.46 mJ/cm2

1.0

0.5

0.0

Δz S

e (

pm

)

1.51.00.50.0

Fluence F (mJ/cm2)

ΔzSe/Δ

F = 0

.538

(7) p

m/(m

J/cm

2 ) 8

4

00.60.40.20.0

Band 1Band 2

ΔE

(m

eV

)

F (mJ/cm2)

ΔE2/Δ

F = 1

6.2(

2.1)

meV

/(mJ/cm

2 )

ΔE 1/ΔF = 10.4(1.4)

meV/(mJ/cm

2 )

5544 mmJJ//cm222

2.0

A

D

B

C

Se

Fe

ΔzSe

ΔE1

Band 1d

xzd

yz

0.30

1.00.80.60.4

Δz

Se (

pm

)

Δt (ps)

0.15

0.0016

12

8

ΔE

1 (me

V)

0.54 mJ/cm2

0.46 mJ/cm2

1.0

0.5

0.0

Δz

Se (

pm

)

1.51.00.50.0

Fluence F (mJ/cm2)

ΔzSe/Δ

F = 0

.538

(7) p

m/(m

J/cm

2 ) 8

4

00.60.40.20.0

Band 1Band 2

ΔE

(m

eV

)

F (mJ/cm2)

ΔE2/Δ

F = 1

6.2(

2.1)

meV

/(mJ/cm

2 )

ΔE 1/ΔF = 10.4(1.4)

meV/(mJ/cm

2 )

5544 mmJJ//cm222

2.0

A

D

B

C

Se

Fe

ΔzSe

ΔE1

Band 1d

xzd

yz

Time-resolved ARPES

Time-resolved XRD (via LCLS)

• A critical parameter important for material property

• Theoretical framework does not exist• Cannot be extracted

quantitatively using conventional techniques (e.g., Raman, optics)

• Can LCLS help ?

Precision measurement not achievable otherwise

Deformation Potential(el-ph coupling)

Time-resolved X-ray diffraction measurement from LCLS

100

90

80

X-r

ay inte

nsity I(Δ

t)/I

0 (%

)

Fourier

am

plit

ude (

a.u

.)

Frequency f (THz)

T = 20 KT = 180 KBackground

5.3 THzA

1g mode

Se

Fe

A1g

zSe

60 unit cellFeSe film

Nb-SrTiO3

substrate

Time delayΔt

8.7 keV x-ray probe

6 eV UV probe

1.5 eV pump

ARPES hemispheredetector

Si photodiode

ARPES hdddetTTime delay

Δtbe

ump

t

3

2

1

0151050 20

A

B

4C

86420Δt (ps)

-8

-4

0

δI(Δ

t)/I

0 (

%)

offset by -6%

100

90

80

X-r

ay inte

nsity I(Δ

t)/I

0 (%

)

Fourier

am

plit

ude (

a.u

.)

Frequency f (THz)

T = 20 KT = 180 KBackground

5.3 THzA

1g mode

Se

Fe

A1g

zSe

60 unit cellFeSe film

Nb-SrTiO3

substrate

Time delayΔt

8.7 keV x-ray probe

6 eV UV probe

1.5 eV pump

ARPES hemispheredetector

Si photodiode

ARPES hdddetTTime delay

Δtbe

ump

t

3

2

1

0151050 20

A

B

4C

86420Δt (ps)

-8

-4

0

δI(Δ

t)/I

0 (

%)

offset by -6%

60 UC FeSe/SrTiO3

• !"#: 5.334 ± 0.001 THzS. Gerber*, S.-L. Yang* et al. Science, 357, 71 (2017)

S. Gerber*, S.-L. Yang* et al. Science, 357, 71 (2017)

DExz/yz/DzSe(meV/pm)DFT -1.6±0.2DMFT -10.3 to -13.4Experiment -13.0 ±2.5

Electron Correlation Modulates the El-Ph

Coupling by an Order of Magnitude

THz-Time Domain Precision Measurement by “THz Lock-In”Electron-Phonon Coupling in Correlated Superconductor FeSe

Time Resolved X-ray Diffraction Tracks Atomic Motion

Time Resolved Photoemission Tracks Electron Energy ChangeMandal et al., Phys. Rev. B.

89, 220502 (R) (2014)Precision measurement not achievable otherwise

Silicon Class Theory

Experiment

….

“Locking-in” to phonons in an uncorrelated material: - Theory

works in uncorrelated Bi2Te3

A1g(1) A1g(2)

Band oscillation

Lattice oscillation

Deformation Potential wrt Bi motion (meV/pm)

Phonon

mode

Theory Experiment

A1g(1) -4.0 -6.4A1g(2) 8.6 11

A1g(1)

A1g(2)

XRD: S.W. Teitelbaum, Y. Huang, T. Sato, M. Chollet, J.M. Glownia, T. Henighan, M. Trigo, D. A. ReisARPES: J.A. Sobota, H. Soifer, P.S. Kirchmann, Z.-X. ShenTheory: J. Querales-Flores, I. Savic, E. Murray, S.B. FahySample synthesis: C. Rotundu, T.P. Bailey, C. Uher

Precision measurement not achievable otherwise

Multimodal Measurements – Sum >> Parts

Re-Cap Use Cases

Time-resolved resonant/non-resonant x-ray diffraction at LCLS

• State of matter not exist otherwise (“driven state”)

• Experimental environment not available otherwise

• Precision measurements not achievable otherwise

LCLS-II Outlook: Resonant inelastic X-ray scattering• Bosonic Mode Information that complements

electronic and structural information:

• Magnon (collective magnetic excitations)• Plasmons (collective charge excitations)• Electron-phonon coupling • Other collective modes…(e.g. Josephson plasmon..)

• RIXS can be a power tool to access to these modes in the energy-momentum-Time domain

• LCLS-II provides much higher photon flux, critical for S/N in photon hungry experiment

• Adding time structure vastly expands the richness of information

Information on Bosonic Modes

LCLS-II Outlook: Ground-state Dynamics of Complex Materials

• Charge, orbital, spin (magnetic) order• Chemical bonding, diffusion, multi-phase• Resonant scattering - element specific• Nano-scale resolution• Photon in/out: in situ/operando, applied fields• Time resolution ~ [Ave. Brightness]2: S/NXPCS ~ t1/2BsX-ray

X-ray Photon Correlation Spectroscopy: Dynamic Structure Factor : S(q,t)Connecting spontaneous fluctuations, dynamics and heterogeneities on multiple length- and time-scales to material properties

XPCS at LCLS-IISequential:• Limited by camera frame rate 2-pulse XPCS:(programmable pulses)• >1 µs ➜ 5 ns (RF buckets) • 1 ps ➜ 10 fs (two-pulse mode) t1 t2 t3

Delay Dt

10-2 10-1 1 10 100Wavenumber (nm-1)

1 µm 100 nm 10 nm 1 nm 1ÅLength Scale

1 eV

1 meV

1 µeV

1 neV

1 peV

1 feV

Ene

rgy

Sca

le

1 fs

1 ps

1 ns

1 µs

1 ms

1 s

Tim

e S

cale Liquids

Glasses

Domainwall

motion

Proteinfolding

Chemicalkinetics

Reaction-Diffusion

SelfAssembly

Spin, lattice,orbital excitations

ChemicalDynamics

Chargeexcitations

LCLS-II

LCLS-II Outlook:High-resolution Mapping of Collective Excitations S(q,w) Û S(q,t)

Can momentum-energy dispersion of elementary excitations be measured directly in the time-domain?

X-ray probe

pump

020

10

50 100 150 200 250 300 350 400 450 5000

0.5

1

1.5

2

2.5

3

3.5

4

-2.5

-2

-1.5

-1

-0.5

0

Ener

gy [m

eV]

• Coherent lattice oscillations in the diffuse X-ray scattering can be used to map out the phonon dispersion

• A new method for mapping nonequilibrium phonon dispersion in momentum-time domain.

M. Trigo et al., Nature Physics, 9, 790 (2013)M.P. Jiang et al., Nature Comm, 7, 12291 (2016) – Ferroelectricity in PbTeS.W. Teitelbaum et al., PRL, 121,125901 (2018) – Bi anharmonic phonon decay

Precision measurement not achievable otherwise

Fourier-transform Inelastic X-ray Scattering

X-ray Photon Correlation (speckle visibility) Spectroscopy

• Two-pulse coherent X-ray scattering reveal nanosecond fluctuations of the topologically-protected skyrmion spin texture

• A new method for mapping stochastic fluctuations and dynamics in the ground-state

M.H. Seaberg, et al., Phys. Rev. Lett. 119, 067403 (2017)

Single chiral skyrmion, with arrows representing the spin direction of the atoms within the spin vortex

delay Dt

Dt1Dt2Dt3

X-ray probes

phononpumping

LCLS-II Outlook: Multimodal Precision Measurement – structure, Fermions and Bosons

PRB

78(2

008)

134

514

PRL

101

(200

8) 0

2640

3

Multiple orbitals require

E- & k-resolved probe

Multiple modes require W- & q-resolved probe

Science 357 (2017) 71 PRL 110 (2013) 265502

trARPES

trXRD (tr)RIXS

ARPES-XRD lock-in• orbital-resolved EPC

• optical modes at G• theory benchmark

! ", $ = & ~()(*

ARPES-XRD lock-in combined with RIXS • compare EPC for optical modes at G• extend EPC measurement to ! $ > &• EPC in novel state of matter through

phonon-pumping in trRIXS

24

Why so hard? – multiple degrees of freedom and complex orders

charge density wave

spin density wave

orbital order

Jahn-Teller distortion

LCLS: Controlling and interrogating matter at unprecedented timescales

plasmon

latticestructure

spinorder

chargeorder

phonon

static ns ps fs

skyrmion magnon

chargetransfer

orbital order

Charge

Spin

Orbital

Lattice

transient superconductivity / Higgs

orbital fluctuations

CDW amplitude mode

Quantum materials

INTERROGATEX-ray probe

CONTROLIR/THz pump

“un-entangle”