On 20 April, 2021, the theory of optical induced spin current in monolayer NbSe2 conducted by Prof. Katsunori Wakabayashi, School of Engineering, has been published in Physical Review B.  

Transition-metal dichalcogenide (TMDC) is a new class of two-dimensional (2D) electronic systems and provides a platform to design the new functional opt-electronic devices. Monolayer NbSe2 is known to show metallic behavior with superconducting phase transition at low temperatures. Owing to the strong atomic spin-orbit coupling (SOC) field, NbSe2 possesses the Ising-type SOC, i.e., an effective Zeeman field that locks electron spin to out-of-plane directions by in-plane momentums.

This article provides numerical results of the spin-dependent optical conductivity of NbSe2 calculated using Kubo formula based on an effective tight-binding model (TBM). It is shown that the up- and down-spin have opposite sign of Hall current, so the pure spin Hall current can be generated in monolayer NbSe2 under light irradiation. The origin of spin current is owing to the topological nature of monolayer NbSe2, i.e., finite spin Berry curvature.  The optically induced spin Hall current can be enhanced by the electron doping and persists even at room temperature. Our results will serve to design opt-spintronics devices such as spin current harvesting by light irradiation based on 2D materials. 

Journal name: Physical Review B
Article title: Optically induced spin current in monolayer NbSe2
Author(s): Ren Habara and Katsunori Wakabayashi
DOI: 10.1103/PhysRevB.103.L161410

Link to the article