Electronic Dynamics Due to Exchange Interaction with Holes in Bulk GaAs

TL;DR

This paper investigates electron-spin dynamics in p-doped GaAs caused by electron-hole exchange interaction, providing numerical results for spin relaxation times and analyzing the effects of screening and non-equilibrium conditions.

Contribution

It offers a detailed numerical analysis of spin relaxation times and extends beyond the relaxation time approximation to include full electron-hole exchange and Coulomb scattering effects.

Findings

Spin relaxation times depend on doping density and temperature.

High-energy electron excitation leads to deviations from simple spin relaxation.

Screening effects are negligible for GaAs but relevant for narrow-gap semiconductors.

Abstract

We present an investigation of electron-spin dynamics in p-doped bulk GaAs due to the electron-hole exchange interaction, aka the Bir-Aronov-Pikus mechanism. We discuss under which conditions a spin relaxation times for this mechanism is, in principle, accessible to experimental techniques, in particular to 2-photon photoemission, but also Faraday/Kerr effect measurements. We give numerical results for the spin relaxation time for a range of p-doping densities and temperatures. We then go beyond the relaxation time approximation and calculate numerically the spin-dependent electron dynamics by including the spin-flip electron-hole exchange scattering and spin-conserving carrier Coulomb scattering at the level of Boltzmann scattering integrals. We show that the electronic dynamics deviates from the simple spin-relaxation dynamics for electrons excited at high energies where the thermalization does not take place faster than the spin relaxation time. We also present a derivation of the influence of screening on the electron-hole exchange scattering and conclude that it can be neglected for the case of GaAs, but may become important for narrow-gap semiconductors.