Spin Hall photoconductance in a 3D topological insulator at room temperature

TL;DR

This study demonstrates room-temperature spin Hall photoconductance in 3D topological insulator Bi2Te2Se, revealing spin accumulation and transport on the surface edges induced by polarized light, with potential for optoelectronic applications.

Contribution

It provides the first evidence of spin Hall photoconductance in 3D topological insulators at room temperature, linking optical excitation to spin transport on the surface edges.

Findings

Helical, bias-dependent photoconductance observed at edges.

Finite Kerr angle indicating spin accumulation.

Spin effects detectable at room temperature.

Abstract

Three-dimensional topological insulators are a class of Dirac materials, wherein strong spin-orbit coupling leads to two-dimensional surface states. The latter feature spin-momentum locking, i.e., each momentum vector is associated with a spin locked perpendicularly to it in the surface plane. While the principal spin generation capability of topological insulators is well established, comparatively little is known about the interaction of the spins with external stimuli like polarized light. We observe a helical, bias-dependent photoconductance at the lateral edges of topological Bi2Te2Se platelets for perpendicular incidence of light. The same edges exhibit also a finite bias-dependent Kerr angle, indicative of spin accumulation induced by a transversal spin Hall effect in the bulk states of the Bi2Te2Se platelets. A symmetry analysis shows that the helical photoconductance is distinct to common longitudinal photoconductance and photocurrent phenomena, but consistent with the accumulated spins being transported in the side facets of the platelets. Our findings demonstrate that spin effects in the facets of 3D topological insulators can be addressed and read-out in optoelectronic devices even at room temperatures.