Ultrafast x ray scattering from coherent phonons
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Ultrafast X-ray Scattering from Coherent Phonons. David A Reis University of Michigan, Department of Physics. International Workshop on Energy Conversion and Information Processing Devices September 26, 2006. Nice, France. How do we understand the interaction

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Ultrafast X-ray Scattering from Coherent Phonons

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Ultrafast x ray scattering from coherent phonons

Ultrafast X-ray Scattering from Coherent Phonons

David A Reis

University of Michigan, Department of Physics

International Workshop on Energy Conversion and Information Processing Devices

September 26, 2006. Nice, France


Ultrafast x ray scattering from coherent phonons

How do we understand the interaction

of an ultrafast laser pulse with condensed matter?

?

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

High Brightness, Picosecond X-rays

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

Laser-pump–X-ray-probe

Ge 400 Bragg reflex.

280 µm thick,vs=5000 m/s

1st

echo

synchrotron

Laser

  • Resolution limited by the bunch duration (or the timing jitter)

  • Arbitrary pump-probe delay

    (NOT limited by bunch separation)

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

Time-resolved Bragg Diffraction:

Coherent Acoustic Phonons

simulation: 100ps & 1.25mdeg conv.

experiment: InSb 111, 10mJ/cm2

D.A. Reis et al.

Reis et al. Phys Rev. Lett.(86) 2001


Ultrafast x ray scattering from coherent phonons

Time-resolved Bragg Diffraction:

Coherent Acoustic Phonons

simulation: 100ps & 1.25mdeg conv.

experiment: InSb 111, 10mJ/cm2

D.A. Reis et al.

Reis et al. Phys Rev. Lett.(86) 2001


Electronic thermal and mechanical properties of thin films and interfaces

Al0.3Ga0.7As

GaAs

AlGaAs

GaAs

AlGaAs

AlGaAs

expansion

expansion

compression

compression

expansion

GaAs

Electronic, Thermal and Mechanical Properties of thin films and interfaces

  • Deformation potential and thermal expansion.

  • Free carrier absorption

  • Electron-phonon

  • Boundary resistance (Kapitza)

  • thermal conductivity and diffusivity.

  • Superlattices and folded phonons

S.H. Lee et al.,PRL 95, 246104 (2005)

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

Fluence dependence

Shows strong saturation

(filling gamma valley)

Early times deformation potential dominates.

non-impulsive component

to strain (Auger heating)

Long times, see heating and

cooling of substrate and film

through shift in Bragg peak due

to thermal expansion

in preparation

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

Coherent Control of Pulsed X-ray Beams

—forward

—deflected

laser

M.F. DeCamp et al., Nature 413, 825 2001

Ambipolar diffusion of dense e-h plasma

M.F. DeCamp et al., Phys. Rev. Lett. 91, 165502, 2003.


Ultrafast x ray scattering from coherent phonons

a

a

a

Bismuth Structure Sensitive to Electronic State

Peierls Distortion

Density Dependent Potential Energy

(Along Trigonal Direction)

What can we learn about interatomic potential through ultrafast optical and x-ray experiments?

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

a

a

a

Femtosecond Optical Pump-Probe

Peierls Distorted

Fritz et al., U. of M.

Coherent A1g Mode is strongly softened and chirped.

anharmonicity or electronic softening? (Fahy and Reis PRL 93 109701, 2004)

D.A. Reis et al.


Coherent control of phonon amplitude at fixed carrier density

coherent control of phonon amplitudeat fixed carrier density

pump1

pump2

chirp independent of phonon amplitude

ultimately optical data cannot measure atomic positions

Murray et al. PRB 72, 060301 (R) 2005.

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

SPPS, LINAC based femtosecond x-rays for Materials research and LCLS R&D.

30 GeV

80 fs 1010, 30 GeV e-/pulse:

80 fs, 9 keV, 106 x rays/pulse


Optical pump probe and aps jitter pulse duration

Optical pump-probe and APSjitter << pulse duration

system response

impulse

delayed probe

pulse

t

SPPS (and future LCLS)jitter >> pulse duration

system response

impulse

time

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

Single-Shot EOS Data at SPPS (100µm ZnTe)

D.A. Reis et al.

A. Cavalieri et al., Phys. Rev. Lett. 94 144801, 2005


Ultrafast x ray scattering from coherent phonons

Electron beam–X-ray beam timing correlation:

EOS and “Melting”

EOS and Melting 60 fs, likely resolution limited.

A. Cavalieri et al., Phys. Rev. Lett. 94 144801, 2005

(fiber transport) S. H. Lee et al. Opt. Lett., 29(22):2602–2604, 2004


Movie of data here

Timing jitter in electron beam used for random sampling

Movie of Data here:

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

x

a

a

a

f

x(t),n(t)

Ultrafast measurement of atomic displacements

N=12463

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

x0

Measured Interatomic Potential of Highly Photoexcited Bismuth

D.M.Fritz Submitted to Science

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

Lee et al, GaAs TDS

Unobserved!

Momentum Resolved Experiments with Diffuse Scattering

Squeezing, phase transitions, anharmonic decay, thermalization…

Biswas and Ambegaokar PRB 26,1980 (1982)

Recoules et al. PRL96,055503 (2006)

D.A. Reis et al.


Phonon dispersion in bi

Phonon Dispersion in Bi

Murray et al. submitted to PRB 2006

D.A. Reis et al.


Ultrafast x ray scattering from coherent phonons

N

S

N

S

N

S

N

S

N

S

N

S

N

S

N

S

N

S

N

2 compressors

S

N

S

N

S

N

S

N

S

N

S

N

S

N

S

N

S

one undulator

LCLS

Future of Ultrafast X-rays, commissioning mid 2008

1.5-15 Å

World’s first x-ray free electron laser

D.A. Reis et al.


Future picosecond x rays at the aps obtaining short x ray pulse from a long electron bunch

Future picosecond X-rays at the APS?Obtaining short x-ray pulse from a “long” electron bunch

RF deflecting cavity

RF deflecting cavity

Electron trajectory

X-ray compression in asymmetric-cut crystals

∆l

Collimating mirror

Radiation from tail electrons

Undulator

Radiation from head electrons

Input x-ray pulse >> diffraction limited size and natural beamsize

A. Zholents

D.A. Reis et al.


Acknowledgments

Acknowledgments

Students

Adrian Cavalieri, David Fritz, Soo-Heyong Lee, Yu-Miin Sheu

APS Sector 7 Staff

Dohn Arms, Eric Dufresne, Eric Landahl, Don Walko

SPPS collaboration

(~13 institutions/50 scientists, J. Hastings spokesperson )

and…

B. Adams, P. Bucksbaum, R. Clarke, M. DeCamp,

R. Goldman, R. Hegde, B. Lings, R. Merilin, E. Murray, S. Fahy, M. Reason, M. Swan, J. Wahlstrand, J. Wark,

…et al.

DOE BES AMOS Program

andStanford PULSE Center

NSF

FOCUS PFC

D.A. Reis et al.


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