Transient Bloch oscillation with the symmetry-governed phase in semiconductor superlattices

Abstract

We have investigated the time evolution of electron transport in the lowest miniband of semiconductor superlattices for various initial electron distributions created by femtosecond laser pulses. It is found that the terahertz wave forms emitted by the transient motion of Bloch oscillating electrons are insensitive to the pump photon energy and that the current starts from its maximum as damped $\text{cos}\text{ }{\ensuremath{\omega}}_{B}t$ (${\ensuremath{\omega}}_{B}$: Bloch frequency), in contrast to the expectation from semiclassical miniband transport. We show that the translationally symmetric electron distribution on the Wannier-Stark ladder is essential for the observed unique oscillation phase.