GHz Spin Noise Spectroscopy in n-Doped Bulk GaAs

TL;DR

This paper introduces an ultrafast spin noise spectroscopy technique to study high-frequency spin dynamics in n-doped GaAs, revealing surface depletion as the main cause of inhomogeneous spin dephasing.

Contribution

It demonstrates a non-demolition optical method to identify the origin of spin dephasing in semiconductors at high frequencies, challenging previous thermal fluctuation explanations.

Findings

Surface electron depletion causes inhomogeneous spin dephasing.

The technique resolves high-frequency spin dynamics.

Dephasing broadening is not due to thermal fluctuations or phonons.

Abstract

We advance spin noise spectroscopy to an ultrafast tool to resolve high frequency spin dynamics in semiconductors. The optical non-demolition experiment reveals the genuine origin of the inhomogeneous spin dephasing in n-doped GaAs wafers at densities at the metal-to-insulator transition. The measurements prove in conjunction with depth resolved spin noise measurements that the broadening of the spin dephasing rate does not result from thermal fluctuations or spin-phonon interaction, as previously suggested, but from surface electron depletion.