Femtosecond to picosecond electron-energy relaxation and Froehlich coupling in quantum dots

TL;DR

This paper presents a theoretical study of electron relaxation in polar semiconductor quantum dots, focusing on phonon interactions and the phonon-bottleneck effect, revealing relaxation times from hundreds of femtoseconds to tens of picoseconds.

Contribution

It introduces a multiphonon state-based theory with self-consistent Tamm-Dancoff approximation to analyze electron relaxation and electron-LO-phonon coupling in quantum dots.

Findings

Relaxation times range from hundreds fs to tens ps.

Relaxation rate shows resonance features but is size-independent.

Electron-LO-phonon coupling significantly influences relaxation dynamics.

Abstract

Electron relaxation in quantum dots is studied theoretically in polar semiconductor materials, with an emphasis put on the phonon-bottleneck problem and electron-LO-phonon coupling. The theory is based on multiphonon states of the electron-LO-phonon system and the self-consistent Tamm-Dancoff approximation is used for the electronic self-energy. Electronic relaxation rate is shown numerically to be on the scale from hundreds fs to tens ps, for electron energy-level separations being in the broad range from about one LO-phonon energy to about three or four optical-phonon energies. Despite of displaying some resonance features, the electronic relaxation rate does not appear to be crucially dependent on the quantum dot size.