Pure Spin Photocurrent in Non-centrosymmetric Crystals: Bulk Spin Photovoltaic Effect

TL;DR

This paper explores the bulk spin photovoltaic effect in non-centrosymmetric crystals, demonstrating how light can generate pure spin currents in various materials, with potential applications in spintronics.

Contribution

It provides a theoretical and computational framework for understanding and predicting the bulk spin photovoltaic effect in diverse non-centrosymmetric materials.

Findings

Pure spin currents can be generated under light in non-centrosymmetric materials.

The effect applies broadly due to the requirement of inversion symmetry breaking.

Theoretical predictions are validated in materials like transition metal dichalcogenides and topological insulators.

Abstract

Spin current generators are critical components for spintronics-based information processing. In this work, we theoretically and computationally investigate the bulk spin photovoltaic (BSPV) effect for creating DC spin current under light illumination. The only requirement for BPSV is inversion symmetry breaking, thus it applies to a broad range of materials and can be readily integrated with existing semiconductor technologies. The BSPV effect is a cousin of the bulk photovoltaic (BPV) effect, whereby a DC charge current is generated under light. Thanks to the different selection rules on spin and charge currents, a pure spin current can be realized if the system possesses mirror symmetry or inversion-mirror symmetry. The mechanism of BPSV and the role of the electronic relaxation time $\tau$ are also elucidated. We apply our theory to several distinct material systems, including transition metal dichalcogenides, anti-ferromagnetic $\rm MnBi_2Te_4$, and the surface of topological crystalline insulator cubic $\rm SnTe$.