Coherent atomic motions in a nanostructure studied by femtosecond X-ray diffraction.
Reversible structural changes of a nanostructure were measured nondestructively with subpicometer spatial and subpicosecond temporal resolution via x-ray diffraction (XRD). The spatially periodic femtosecond excitation of a gallium arsenide/aluminum gallium arsenide superlattice results in coherent lattice motions with a 3.5-picosecond period, which was directly monitored by femtosecond x-ray pulses at a 1-kilohertz repetition rate. Small changes (DeltaR/R = 0.01) of weak Bragg reflexes (R = 0.005) were detected. The phase and amplitude of the oscillatory XRD signal around a new equilibrium demonstrate that displacive excitation of the zone-folded acoustic phonons is the dominant mechanism for strong excitation.
Bargheer
M
M
Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
Zhavoronkov
N
N
Gritsai
Y
Y
Woo
J C
JC
Kim
D S
DS
Woerner
M
M
Elsaesser
T
T