Multi-subband effect in spin dephasing in semiconductor quantum wells

TL;DR

This study investigates how multi-subband interactions influence spin dephasing in GaAs quantum wells, revealing that strong inter-subband scattering leads to similar spin dynamics across subbands and that well width, temperature, and electric field significantly affect spin coherence times.

Contribution

It provides a comprehensive analysis of multi-subband effects on spin dephasing, incorporating electron-electron and electron-phonon scattering in quantum wells.

Findings

Inter-subband scattering causes similar spin dephasing rates across subbands.

Spin dephasing time increases with temperature and electric field in narrow wells.

In wide wells, spin dephasing time decreases with temperature and electric field.

Abstract

Multi-subband effect on spin precession and spin dephasing in $n$-type GaAs quantum wells is studied with electron-electron and electron-phonon scattering explicitly included. The effects of temperature, well width and applied electric field (in hot-electron regime) on the spin kinetics are thoroughly investigated. It is shown that due to the strong inter-subband scattering, the spin procession and the spin dephasing rate of electrons in different subbands are almost identical despite the large difference in the D'yakonov-Perel' (DP) terms of different subbands. It is also shown that for quantum wells with small well width at temperatures where only the lowest subband is occupied, the spin dephasing time increases with the temperature as well as the applied in-plane electric field until the contribution from the second subband is no longer negligible. For wide quantum wells the spin dephasing time tends to decrease with the temperature and the electric field.