Probing unfolded acoustic phonons with X rays.
Ultrafast laser excitation of an InGaAs/InAlAs superlattice (SL) creates coherent folded acoustic phonons that subsequently leak into the bulk (InP) substrate. Upon transmission, the phonons become "unfolded" into bulk modes and acquire a wave vector much larger than that of the light. We show that time-resolved x-ray diffraction is sensitive to this large-wave vector excitation in the substrate. Comparison with dynamical diffraction simulations of propagating strain supports our interpretation.
Trigo
M
M
Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA. mtrigo@umich.edu
Sheu
Y M
YM
Arms
D A
DA
Chen
J
J
Ghimire
S
S
Goldman
R S
RS
Landahl
E
E
Merlin
R
R
Peterson
E
E
Reason
M
M
Reis
D A
DA