Transient Magnetoresponse of Photoexcited Electrons: Oscillating Conductivity and Negative Cyclotron Absorption

Abstract

The nonlinear transient magnetoresponse of two-dimensional (2D) electrons is studied theoretically. Transient conductivity is calculated under exact cyclotron resonance condition. Two cases are considered: (a) the electrons excited by an ultrashort optical pulse, and isotropy of the initial distribution is expected; (b) dc electric field impose strongly anisotropic initial distribution. In case (b), evolution is strongly dependent on the initial phase of a circularly polarized wave. After the streaming distribution is formed, the magnetoresponse demonstrates periodically oscillating conductivity for both cases. The negative cyclotron absorption caused by the transient absolute negative conductivity effect is predicted for a certain range of parameters.