Time-resolved X-Ray diffraction from coherent phonons during a laser-induced phase transition
Time-resolved x-ray diffraction with picosecond temporal resolution is used to observe scattering from impulsively generated coherent acoustic phonons in laser-excited InSb crystals. The observed frequencies and damping rates are in agreement with a model based on dynamical diffraction theory coupled to analytic solutions for the laser-induced strain profile. The results are consistent with a 12 ps thermal electron-acoustic phonon coupling time together with an instantaneous component from the deformation-potential interaction. Above a critical laser fluence, we show that the first step in the transition to a disordered state is the excitation of large amplitude, coherent atomic motion.
Lindenberg
AM
Department of Physics, University of California, Berkeley, California 94720, USA.
Kang
I
Johnson
SL
Missalla
T
Heimann
PA
Chang
Z
Larsson
J
Bucksbaum
PH
Kapteyn
HC
Padmore
HA
Lee
RW
Wark
JS
Falcone
RW