Radiation-Induced "Zero-Resistance State" and the Photon Assisted Transport

We demonstrate that the radiation induced "zero-resistance state" observed in a two-dimensional electron gas is a result of the non-trivial structure of the density of states of the systems and the photon assisted transport. A toy model of a structureless quantum tunneling junction where the system has oscillatory density of states catches most of the important features of the experiments. We present a generalized Kubo-Greenwood conductivity formula for the photon assisted transport in a general system, and show essentially the same nature of the transport anomaly in a uniform system.