Thermal escape and capture processes in quantum wire–dot structures

Abstract

We study the dynamics of an electronic wave packet in a quantum wire with an embedded quantum dot interacting with an LO-phonon bath at room temperature. Two different cases are studied: in the first scenario (escape scenario), we determine the probability for the electrons to leave the dot by absorption of an LO-phonon. In the second scenario (capture and escape scenario), we study the capture process from the delocalized states of the wire into the localized states of the dot accompanied by re-emission into the delocalized states. These scenarios are analysed by using a quantum kinetic theory for the electron LO-phonon interaction. The thermal escape scenario shows a continuous flow of density directed with equal probabilities to both sides from the dot accompanied by small oscillations in the density of bound carriers. For the capture and escape scenario, we find an interplay between thermal escape and a coherent escape process, the latter being present even at zero temperature. In the coherent escape, a part of the captured density re-escapes and forms additional travelling wave packets following the original wave packet.