Dephasing of terahertz Bloch oscillations in a GaAs-based narrow-minigap superlattice excited by tunable pump photon energy

Abstract

Abstract We investigate peculiar Bloch oscillations under interminiband mixing in a GaAs-based narrow-minigap superlattice by terahertz emission spectroscopy. The dephasing time decreases with increasing pump photon energy and drops substantially at a certain energy, in contrast to that reported for Wannier–Stark ladder states in a nearly isolated miniband. This behavior can be ascribed to the LO phonon emission of electrons that are excited with in-plane excess energies and accelerated under dc bias electric field in the conduction first miniband. Our findings support the validity of the miniband transport model employed recently to account for an accompanying π/2 shift in the oscillation phase.