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

Area of Science:

• Condensed Matter Physics
• Spintronics
• Terahertz Spectroscopy

Background:

• The spin Hall effect (SHE) is crucial for spintronics, but its frequency-dependent behavior and underlying mechanisms remain incompletely understood.
• Investigating SHE across different frequency regimes, from DC to THz, is essential for elucidating its origins and potential applications.

Purpose of the Study:

• To experimentally determine the spin Hall conductivity (SHC) spectrum in Gallium Arsenide (GaAs) at room temperature.
• To compare experimental results with theoretical predictions and identify the dominant mechanisms contributing to SHE across different frequency ranges.

Main Methods:

• Utilized terahertz (THz) polarimetry with high precision (several μrads) to measure Faraday rotation.
• Employed optical injection of spin-polarized electrons to probe the inverse spin Hall effect (ISHE).

Main Results:

• Successfully observed and measured the SHC spectrum in GaAs at room temperature.
• Demonstrated excellent quantitative agreement between the experimental SHC spectrum and theoretical models.
• Identified a crossover in the dominant SHC mechanism: impurity scattering at low frequencies (DC regime) and the intrinsic Berry curvature mechanism at THz frequencies.

Conclusions:

• The study provides the first experimental spectrum of spin Hall conductivity in GaAs.
• The findings validate theoretical models and highlight the distinct contributions of impurity scattering and Berry curvature to SHE.
• The developed THz spectroscopic technique offers a novel approach for studying anomalous transport phenomena related to various degrees of freedom.