Symmetry manipulation of nonlinear optical effect for metallic transition-metal dichalcogenides

Nonlinear optical (NLO) effect plays a crucial role to engineer optical angular frequency , symmetry of electronic system. Metallic transition-metal dichalcogenides are one of two-dimensional (2D) materials, which have no inversion symmetry for odd-number layers. In particular, odd-number-layered NbSe2 has spin splitting owing to Ising-type spin-orbit coupling. In this paper, we numerically calculate the NLO charge and spin conductivities of NbSe2 based on an effective tight-binding model for several different optical effects, i.e., symmetry manipulation by bicircular light (BCL) and bulk photovoltaic effect (shift and injection currents). Under irradiation of BCL which can control the symmetry of electronic system, the current can be generated even in even-number-layered NbSe2. Also, we find that shift current can be generated for odd-number-layered NbSe2, which is robust against electronic scattering, i.e., topological current. The direction of generated shift current can be switched by altering polarization of light. Our results will serve to design opto-spintronics devices based on 2D materials to manipulate the charge and spin currents and their directions by controlling the polarization of incident light which recasts the symmetry of electronic systems.

Automated summary

In this study, the nonlinear optical and spin conductivities of NbSe2 are numerically calculated using an effective tight-binding model, considering different optical effects such as symmetry manipulation and bulk photovoltaic effect. The results demonstrate that by controlling the polarization of light, current can be generated and its direction can be altered. This finding is significant for the design of opto-spintronic devices based on 2D materials.