Resonant photovoltaic effect of doped semiconductors

The rectified non-linear response of a clean, time-reversal symmetric, undoped semiconductor to an ac electric field includes a wellknown intrinsic shift current. We show that when Kramers degeneracy is broken, a distinct second-order rectified response appears due to Bloch state anomalous velocities in a system with an oscillating Fermi surface. This effect, which we refer to as the resonant photovoltaic effect (RPE), produces a resonant galvanic current peak at the interband absorption threshold in doped semiconductors or semimetals with approximate particle-hole symmetry. In this talk, I will present this new non-linear RPE effect and will discuss it for a model of the surface states of a magnetized topological insulator.