Pure spin photocurrent in non-centrosymmetric crystals: bulk spin photovoltaic effect

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 BSPV 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 BSPV and the role of the electronic relaxation time tau are also elucidated. We apply our theory to several distinct materials, including monolayer transition metal dichalcogenides, anti-ferromagnetic bilayer MnBi2Te4, and the surface of topological crystalline insulator cubic SnTe. Light offers a fast and non-invasive way to generate spin-currents in materials, however, this typically requires special ingredients such as magnetic materials, or circularly polarised light. In this theory work, the authors show how the nonlinear optical effect can generate a spin current, with the only requirement being broken inversion symmetry.

Automated summary

In this study, the researchers investigate the bulk spin photovoltaic (BSPV) effect for generating DC spin current under light illumination. They demonstrate that a pure spin current can be realized if the system possesses mirror symmetry or inversion-mirror symmetry, with the only requirement being broken inversion symmetry. This offers a fast and non-invasive way to generate spin-currents in materials, potentially expanding the possibilities for spintronics-based information processing.