Pauli blockade of the electron spin flip in bulk GaAs

TL;DR

This study measures how electron spin-flip times in undoped GaAs vary with kinetic energy and excitation density, revealing phase-space filling effects that significantly prolong spin relaxation times.

Contribution

It provides the first experimental determination of the k-dependence of electron spin-flip times in bulk GaAs and demonstrates phase-space filling effects through Monte-Carlo simulations.

Findings

Spin-flip time decreases with increasing electron kinetic energy.

Phase-space filling effects block spin flips, increasing t_sf with excitation density.

Longest reported spin-relaxation time in undoped GaAs without magnetic field.

Abstract

By means of time-resolved optical orientation under strong optical pumping, the k-dependence of the electron spin-flip time (t_sf) in undoped GaAs is experimentally determined. t_sf monotonically decreases by more than one order of magnitude when the electron kinetic energy varies from 2 to 30 meV. At the high excitation densities and low temperatures of the reported experiments the main spin-flip mechanism of the conduction band electrons is the Bir-Aronov-Pikus. By means of Monte-Carlo simulations we evidence that phase-space filling effects result in the blocking of the spin flip, yielding an increase of t_sf with excitation density. These effects obtain values of t_sf up to 30 ns at k=0, the longest reported spin-relaxation time in undoped GaAs in the absence of a magnetic field.