Enhanced Faraday rotation and control of pure spin-valley optical conductivity by topological phase in silicene

Abstract

We investigate the Faraday rotation and optical conductivity in silicene under applying staggered exchange and perpendicular electric field. In silicene, combination of buckled atomic structure and strong spin orbit interaction (SOI) gives rise to electrons in the system behaving like 2-dimensional Dirac fermion with controllable mass. The Faraday rotation occurs when polarized light is passing through the silicene plane is calculated. The Faraday rotation related to topological phases is mainly focused. As a result, it is found that the presence of both exchange and electric fields is required to generate the Faraday rotation effect. The spin-valley dependent Dirac mass plays the role of the parameters to suppress the Faraday rotation. The Hall conductivity and Faraday rotation are still observed under the topological phases only in the cases of quantum anomalous Hall (QAH) and semimetal phase (SM), because their total Chern numbers do not go to zero. The very large angle is predicted for some specific electric and exchange field strengths. The perfect spin-valley filtered that only one electron specie is allowed to transport is also predicted in topological phase transition. This paves the way to perfectly control the pure spin-valley longitudinal current and to be applicable for beneficial spin-valley optoelectronic devices . • Faraday rotation (FR) and optical conductivity under topological phases in silicene is studied. • The presence of both exchange and electric staggered potentials is required to create FR. • FR is found at low photon frequency due only to the presence of quantum anomalous Hall and semimetal phases. • Large FR is enhanced by the presence of spin-valley dependent mass of Dirac fermions. • The controllable pure spin-valley current by photon frequency is related to topological phase transition.