Effects of tilted Dirac cones and in-plane electric field on the valley-dependent magneto-optical absorption spectra in monolayer 8–Pmmn borophene

Abstract

We investigate the optical absorption properties in a 8-Pmmn borophene monolayer with anisotropic tilted Dirac cones, subjected to a perpendicular magnetic field and in-plane dc electric field (EF). Numerical results for the magneto-optical absorption coefficient (MOAC) show that the tilt of the Dirac cones causes the redshift of absorption peaks. More interestingly, there appears minor absorption peaks corresponding to the transitions between the Landau levels (LLs) n and n±2 beside the principal maxima corresponding to the transitions between LLs n and n±1. These minor peaks are absent in other two-dimensional Dirac materials with non-titled Dirac cones. The simultaneous presence of in-plane EF and the tilt parameter in 8–Pmmn borophene lifts the valley degeneracy in the LLs and causes the valley polarization in the MOAC, that do not occur in the absence of in-plane EF and/or the tilt parameter. The valley-polarized MOAC opens up potential applications in valleytronics.