Observation of Terahertz Spin Hall Conductivity Spectrum in GaAs with Optical Spin Injection

TL;DR

This paper presents the first room-temperature measurement of the spin Hall conductivity spectrum in GaAs using terahertz polarimetry, revealing a crossover from impurity scattering to Berry-curvature mechanisms.

Contribution

It introduces a novel spectroscopic technique to measure spin Hall conductivity spectra at terahertz frequencies, confirming theoretical predictions in GaAs.

Findings

Spin Hall conductivity spectrum observed at room temperature.

Excellent agreement with theoretical models.

Crossover from impurity scattering to Berry-curvature mechanism.

Abstract

We report the first observation of the spin Hall conductivity spectrum in GaAs at room temperature. Our terahertz polarimetry with a precision of several $\mu$rads resolves the Faraday rotation of terahertz pulses arising from the inverse spin Hall effect of optically injected spin-polarized electrons. The obtained spin Hall conductivity spectrum exhibits an excellent quantitative agreement with theory, demonstrating a crossover in the dominant origin from impurity scattering in the DC regime to the intrinsic Berry-curvature mechanism in the terahertz regime. Our spectroscopic technique opens a new pathway to analyze anomalous transports related to spin, valley, or orbital degrees of freedom.