Spin oscillations and Zitterbewegung of free carriers in semiconductors (Conference Presentation)

Abstract

We discuss the results of recent theoretical and experimental study of coupled spin-charge dynamics and noise of free carriers in three- and two-dimensional semiconductor structures. (i) Due to the Brownian motion of electrons and spin-orbit interaction, the temporal and spatial correlations of spin fluctuations emerging in the electron gas are coupled and the fluctuations probed at spatially separated spots of the sample are correlated. The spin correlations at large delay times are determined by the long-lived waves of spin density and drastically increase in the regime of a persistent spin helix. The measurement of spatial spin fluctuations provides direct access to the parameters of spin-orbit coupling and spin transport in conditions close to thermal equilibrium. (ii) The spin precession of electrons in a magnetic field gives rise to a trembling orbital motion of the carriers, a phenomenon similar to Zitterbewegung that free relativistic particles can experience. The trembling motion emerges in the absence of an ac driving force and caused by a quantum interference between the spin split states. The phenomenon can be studied by measuring the macroscopic ac electric current of the coherent trembling motion of spin-polarized electrons or, alternatively, by detecting the electric noise at the frequency of the Larmor precession at thermal equilibrium.