Control of carrier transport in GaAs by longitudinal-optical phonon-carrier scattering using a pair of laser pump pulses

Abstract

We demonstrate optical control of the LO phonon-plasmon coupled (LOPC) modes in GaAs by using a femtosecond pump-pulse pair. The relaxation time of the plasmonlike LOPC mode significantly depends on the separation time (Dt) of the pump-pulse pair. Especially it is maximized when Dt becomes simultaneously comparable to the half period of the longitudinal optical (LO) phonon oscillation and resonant to the 3/4 period of the plasmonlike LOPC oscillation. We attribute these observations to the modification of carrier-LO phonon scattering and ballistic motion of the plasmonlike LOPC mode.

Ultrafast optical excitation of coherent phonons in a one-dimensional metal at the photoinduced insulator-metal transition

“…1,2 According to an advancement of the femtosecond (fs) laser technology, an optical pumping with a shorter pulsed laser than a phonon period was found to lead to the coherent oscillation (i.e., coherent phonons) in the optical properties such as reflectivity or transmission. 3 Coherent phonons drive abundant physics such as many-body interferences singular at the onset of quasiparticle, 4,5 or possibilities for controlling coupled degrees of freedom in the ultrafast time span in semiconductors [6][7][8] and superconductors. 9 Generation of coherent phonons is also observed in a broad class of the photoinduced insulator-metal transitions (PIMTs) accompanying the structural changes in terms of the melting of the lattice-induced order.…”