Optically-modulated edge states and resonant tunneling based on valley-Zeeman spin–orbit coupling

Abstract

The valley-Zeeman spin–orbit coupling (VZSOC) in graphene provides a platform to discover novel edge states and enrich the quantum transport phenomena. In this work, based on the VZSOC induced helical edge states regarded as two copies of chiral edge states, we investigate the modulation of the edge state and corresponding resonant tunneling with the well-defined transmission peaks under off-resonant circularly polarized (ORCP) light. It shows that the spin-up or spin-down chiral edge state can be transformed into two types of antichiral edge state where the edge states propagate in the same direction at two parallel boundaries and the bulk states propagate in opposite direction, and reversed chiral edge states by the intensity and polarized direction of the ORCP light, finally leading to fascinated edge states. These edge-state transitions are attributed to regulating the Dirac gaps by the ORCP light. Particularly, some novel resonant tunneling in junctions consisting of different edge states are discovered, most of which can be intuitively understood as different types of the loop currents that the current flows in a loop. Interestingly, the combined effect of the backscattering and loop current also plays an important role in generating resonant tunneling. These results provide a new view to manipulate helical edge state induced by the VZSOC and understand rich physics of the resonant tunneling by the loop current.