title: Probing unfolded acoustic phonons with X rays.
abstract: 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.
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA. mtrigo@umich.edu
authors.forename: M
authors.initials: M
authors.lastname: Trigo
authors.forename: Y M
authors.initials: YM
authors.lastname: Sheu
authors.forename: D A
authors.initials: DA
authors.lastname: Arms
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: S
authors.initials: S
authors.lastname: Ghimire
authors.forename: R S
authors.initials: RS
authors.lastname: Goldman
authors.forename: E
authors.initials: E
authors.lastname: Landahl
authors.forename: R
authors.initials: R
authors.lastname: Merlin
authors.forename: E
authors.initials: E
authors.lastname: Peterson
authors.forename: M
authors.initials: M
authors.lastname: Reason
authors.forename: D A
authors.initials: DA
authors.lastname: Reis