Photon dressed electronic states in topological insulators: Tunneling and conductance

The surface bound electronic states of three-dimensional topological insulators, as well as the edge states in two-dimensional topological insulators, are investigated in the presence of a circularly polarized light. The strong coupling between electrons and photons is found t o give rise to an energy gap as well as a unique energy dispersion of the dressed states, different from both graphene and conventional two-dimensional electron gas (2DEG). The effects of electron-photon interaction, barrier height and width on the electron tunneling through a p-n junction and on the ballistic conductance in topological insulators are demonstrated by numerical calculations. A critical energy for an incident electron to tunnel perfectly through a barrier is predicted, where electrons behave as either massless Dirac-like or massive Schrodinger-like particles above or below this threshold value. Additionally, these effects are compared with those in zigzag graphene nanoribbons and a 2DEG. Both the similarities and the differences are demonstrated and explained.