Spin relaxation times of 2D holes from spin sensitive bleaching of inter-subband absorption

TL;DR

This study measures spin relaxation times of 2D holes in GaAs/AlGaAs quantum wells using spin sensitive bleaching, revealing dependence on quantum well width and temperature, and identifying the D'yakonov-Perel' mechanism as dominant.

Contribution

It introduces a method to determine hole spin relaxation times via spin sensitive bleaching of inter-subband absorption in quantum wells, highlighting the influence of quantum well width and temperature.

Findings

Spin relaxation times decrease with narrower quantum wells.

D'yakonov-Perel' mechanism governs hole spin relaxation.

Saturation intensity varies significantly with quantum well width.

Abstract

We present spin relaxation times of 2D holes obtained by means of spin sensitive bleaching of the absorption of infrared radiation in p-type GaAs/AlGaAs quantum wells (QWs). It is shown that the saturation of inter-subband absorption of circularly polarized radiation is mainly controlled by the spin relaxation time of the holes. The saturation behavior has been determined for different QW widths and in a wide temperature range with the result that the saturation intensity substantially decreases with narrowing of the QWs. Spin relaxation times are derived from the measured saturation intensities by making use of calculated (linear) absorption coefficients for direct inter-subband transitions. It is shown that spin relaxation is due to the D'yakonov-Perel' mechanism governed by hole-hole scattering. The problem of selection rules is addressed.