Measurement of spin diffusion in semi-insulating GaAs

TL;DR

This study measures spin diffusion in semi-insulating GaAs using optical transient-grating spectroscopy, revealing a temperature-independent diffusion coefficient and demonstrating how spin diffusion can estimate electron diffusion, influenced by electron-electron interactions.

Contribution

First measurement of spin diffusion coefficient in semi-insulating GaAs across a range of temperatures using optical methods.

Findings

Spin diffusion coefficient is approximately 88 cm²/s from 15 K to 150 K.

Spin diffusion length is at least 450 nm.

Electron diffusion is 1.4 times larger than spin diffusion due to electron-electron interactions.

Abstract

We use optical transient-grating spectroscopy to measure spin diffusion of optically oriented electrons in bulk, semi-insulating GaAs(100). Trapping and recombination do not quickly deplete the photoexcited population. The spin diffusion coefficient of 88 +/- 12 cm2/s is roughly constant at temperatures from 15 K to 150 K, and the spin diffusion length is at least 450 nm. We show that it is possible to use spin diffusion to estimate the electron diffusion coefficient. Due to electron-electron interactions, the electron diffusion is 1.4 times larger than the spin diffusion.