Electrically tunable nonlinear Faraday ellipticity and rotation in WTe2

There has been considerable interest in the nonlinear optical phenomenon in recent years, particularly in two-dimensional materials. Here, we study the optical polarization quantities namely ellipticity and Faraday rotation for the monolayer 1T ′ -WTe 2 two-dimensional (2D) material. We develop a new general approach based on many-body perturbation theory to compute polarization quantities via the second harmonic susceptibility of the material. We find that the nonlinear second-harmonic longitudinal and transverse responses are tunable with the inclination angle made by the out-of-plane field with an axis vertical to the 2D plane. This field breaks the inversion symmetry of the system which is an essential condition for the behavior of the second harmonic susceptibility. Such tunable behavior gives significant variation to the Faraday rotation and ellipticity. Our findings provide valuable information for future experiments on the optical phenomenon in 2D materials.