| Umklapp process in observation of coherent folded longitudinal acoustic phonons in a GaAs/AlAs long-period superlattice (2004) | |||||||||||||
Abstract | |||||||||||||
| Coherent folded longitudinal acoustic phonons in a GaAs/AlAs long-period superlattice (SL) have been investigated by using a reflection-type two-color pumpprobe technique under the condition that the wave vector of the probe pulse in the sample exceeds the mini-Brillouin zone. The coherent oscillations observed in the time-domain signals indicate the propagation of the phonon wave packet through the whole SL layer. The Fourier transform spectrum of the time-domain signals is compared with the dispersion relation of the folded longitudinal acoustic phonons in the long-period SL calculated using a transfer matrix method on the bases of an elastic continuum model. This comparison indicates that the folded longitudinal acoustic phonons in the long-period SL are observed through the umklapp process. | |||||||||||||
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