Transcript Of picoseconds and picometers: ultrafast x rays in

FOCU S
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
of an ultrafast laser pulse with condensed matter?
?
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High Brightness, Picosecond X-rays
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Laser-pump–X-ray-probe
synchrotron
Laser
Ge 400 Bragg reflex.
280 µm thick,vs=5000 m/s
•Resolution limited by the bunch
duration (or the timing jitter)
•Arbitrary pump-probe delay
(NOT limited by bunch separation)
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1st
echo
Time-resolved Bragg Diffraction:
Coherent Acoustic Phonons
experiment: InSb 111, 10mJ/cm2
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simulation: 100ps & 1.25mdeg conv.
Reis et al. Phys Rev. Lett.(86) 2001
Time-resolved Bragg Diffraction:
Coherent Acoustic Phonons
experiment: InSb 111, 10mJ/cm2
D.A. Reis et al.
simulation: 100ps & 1.25mdeg conv.
Reis et al. Phys Rev. Lett.(86) 2001
Electronic, Thermal and Mechanical Properties of
thin films and interfaces •Deformation potential and
Al0.3Ga0.7As
thermal expansion.
•Free carrier absorption
•Electron-phonon
GaAs
AlGaAs
GaAs
•Boundary resistance
(Kapitza)
•thermal conductivity and
diffusivity.
•Superlattices and folded
phonons
AlGaAs
AlGaAs
expansion
compression
expansion
compression
expansion
GaAs
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S.H. Lee et al., PRL 95, 246104 (2005)
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
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Coherent Control of Pulsed X-ray Beams
—forward
—deflected
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.
Bismuth Structure Sensitive to Electronic State
Peierls Distortion
Density Dependent Potential Energy
(Along Trigonal Direction)
a
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What can we learn about interatomic potential through
ultrafast optical and x-ray experiments?
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Femtosecond Optical Pump-Probe
Peierls Distorted
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a
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a
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)
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coherent control of phonon amplitude
at fixed carrier density
pump1
pump2
chirp independent of phonon amplitude
ultimately optical data cannot measure atomic positions
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Murray et al. PRB 72, 060301 (R) 2005.
SPPS, LINAC based femtosecond x-rays
for Materials research and LCLS R&D.
80 fs 1010, 30 GeV e-/pulse:
80 fs, 9 keV, 106 x rays/pulse
Optical pump-probe and APS
jitter << pulse duration
impulse
system response
delayed probe
pulse
S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 t
impulse
system response
SPPS (and future LCLS)
jitter >> pulse duration
S1
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S9
S4
S7
S6
S3
S8
S0
S5
S2 time
Single-Shot EOS Data at SPPS (100µm ZnTe)
100 um
ZnTe
ultrafast laser
 ~ 200 fs
electrons
v~c
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A. Cavalieri et al., Phys. Rev. Lett. 94 144801, 2005
Electron beam–X-ray beam timing correlation:
EOS and “Melting”
EOS and Melting 
limited.
60 fs, likely resolution
A. Cavalieri et al., Phys. Rev. Lett. 94 144801, 2005
(fiber transport) S. H. Lee et al. Opt. Lett., 29(22):2602–2604, 2004
Timing jitter in electron beam used for random sampling
Movie of Data here:
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
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Ultrafast measurement of atomic displacements
N=12463
x
a
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f
x(t),n(t)
Measured Interatomic Potential of Highly Photoexcited Bismuth
x0
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D.M.Fritz Submitted to Science
Momentum Resolved Experiments with Diffuse Scattering
Squeezing, phase transitions, anharmonic decay, thermalization…
Lee et al, GaAs TDS
Unobserved!
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Biswas and Ambegaokar PRB 26,1980 (1982)
Recoules et al. PRL 96, 055503 (2006)
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Phonon Dispersion in Bi
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Murray et al. submitted to PRB 2006
Future of Ultrafast X-rays, commissioning mid 2008
1.5-15 Å
LCLS
2 compressors
S
N S
N S
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N S
N S
N S
N S
N S
N S
N S
N S
one undulator
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World’s first x-ray free electron laser
N S
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N
N S
Future picosecond X-rays at the APS?
Obtaining short x-ray pulse from a “long” electron bunch
yz   z  
eU
Ebeam
RF deflecting cavity
 rf 2 z
 undul rf
RF deflecting cavity
Electron
trajectory
X-ray compression in
asymmetric-cut crystals
Radiation from tail electrons
Collimating
mirror
∆l
  y2'   x2ray
Undulator
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Radiation from head electrons
Input x-ray pulse >> diffraction
limited size and natural beamsize
A. Zholents
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
and Stanford PULSE Center
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NSF
FOCUS PFC