Ultrahigh Bandwidth Spin Noise Spectroscopy: Detection of Large g-Factor Fluctuations in Highly n-Doped GaAs

TL;DR

This paper introduces an ultrafast, all-optical spin noise spectroscopy method capable of detecting large g-factor fluctuations in highly n-doped GaAs at hundreds of gigahertz bandwidths, revealing intrinsic dopant-related variability.

Contribution

The authors develop a novel ultrafast SNS technique using pulse trains from laser oscillators, enabling high-bandwidth, minimally perturbative measurements of spin dynamics in semiconductors.

Findings

Detection of large g-factor fluctuations in n-doped GaAs.

Fluctuations are intrinsic, not due to sample imperfections.

Technique achieves hundreds of gigahertz detection bandwidth.

Abstract

We advance all optical spin noise spectroscopy (SNS) in semiconductors to detection bandwidths of several hundred gigahertz by employing an ingenious scheme of pulse trains from ultrafast laser oscillators as an optical probe. The ultrafast SNS technique avoids the need for optical pumping and enables nearly perturbation free measurements of extremely short spin dephasing times. We employ the technique to highly n-doped bulk GaAs where magnetic field dependent measurements show unexpected large g-factor fluctuations. Calculations suggest that such large g-factor fluctuations do not necessarily result from extrinsic sample variations but are intrinsically present in every doped semiconductor due to the stochastic nature of the dopant distribution.