Stochastic Faraday rotation induced by the electric current fluctuations in nanosystems

摘要

We demonstrate theoretically that in gyrotropic semiconductors and semiconductor nanosystems the Brownianmotion of electrons results in temporal fluctuations of the polarization plane of light passing through or reflectedfrom the structure, i.e., in stochastic Faraday or Kerr rotation effects. The theory of the effects is developed fora number of prominent gyrotropic systems such as bulk tellurium, ensembles of chiral carbon nanotubes, andGaAs-based quantum wells of different crystallographic orientations. We show that the power spectrum of thesefluctuations in thermal equilibrium is proportional to the ac conductivity of the system.We evaluate contributionsresulting from the fluctuations of the electric current, as well as of spin, valley polarization, and the spin currentto the noise of the Faraday/Kerr rotation. Hence all-optical measurements of the Faraday and Kerr rotation noiseprovide an access to the transport properties of the semiconductor systems.