Radiation-induced magnetoresistance oscillations in a 2D electron gas

Remarkable recent experiments have shown that microwave radiation can induce dramatic changes in the DC transport properties of a high mobility two-dimensional electron gas. In particular, the diagonal resistivity is an oscillatory function of ω/ω_c, where ω is the microwave frequency and ω_c is the cyclotron frequency. The amplitude of the oscillations increases with microwave intensity and eventually saturates as the minimum resistivity approaches zero. We describe a simple model, first proposed many years ago by Ryzhii and collaborators, to explain the effect, and present simplified but detailed and non-perturbative calculations of the non-equilibrium response of the electron gas. We also review some of the many different theoretical pictures that have been proposed to explain the physics and discuss open questions which remain.