# Listening to the spin noise of conduction electrons in bulk n:GaAs - Condensed Matter > Mesoscale and Nanoscale Physics

Abstract: We report a comprehensive study of stochastic electron spin fluctuations -spin noise - in lightly doped $n$-type bulk GaAs, which are measured usingsensitive optical magnetometry based on off-resonant Faraday rotation.Frequency spectra of electron spin noise are studied as a function of electrondensity, magnetic field, temperature, probe laser wavelength and intensity, andinteraction volume. Electron spin lifetimes $\tau s$ are inferred from thewidth of the spin noise spectra, and are compared with direct measurements of$\tau s$ using conventional Hanle effect methods. Both methods reveal a strongand similar dependence of $\tau s$ on the wavelength and intensity of the probelaser, highlighting the undesired influence of sub-bandgap absorption effectson the nominally `non-perturbative- spin noise measurements. As a function oftemperature, the spin noise power increases approximately linearly from 1.5 Kto 30 K, as expected for degenerate electrons obeying Fermi-Dirac statistics,but with an additional zero-temperature offset. Finally, as the cross-sectionalarea of the probe laser shrinks and fewer electrons are probed, the measuredFaraday rotation fluctuations due to electron spin noise are shown to increase,as expected.

Author: S. A. Crooker, L. Cheng, D. L. Smith

Source: https://arxiv.org/