Spin noise spectroscopy of randomly moving spins in the model of light scattering: Two-beam arrangement

TL;DR

This paper provides an exact analytical solution for spin-noise signals in a medium with moving spins, highlighting how a two-beam setup can reveal spin dynamics and correlations, but also showing diffusion can suppress the signal.

Contribution

It introduces a novel analytical approach to spin-noise spectroscopy in two-beam arrangements, accounting for spin diffusion effects on the signal.

Findings

Two-beam arrangement enhances sensitivity to spin motion and correlations.

Spin diffusion can significantly suppress the spin-noise signal.

Suppression mechanism is similar to time-of-flight broadening.

Abstract

A strict analytical solution of the problem of spin-noise signal formation in a volume medium with randomly moving spin carriers is presented. The treatment is performed in the model of light scattering in a medium with fluctuating inhomogeneity. Along with conventional single-beam, geometry, we consider the two-beam arrangement, with the scattering field of the auxiliary ("tilted") beam heterodyned on the photodetector illuminated by the main beam. It is shown that the spin noise signal detected in the two-beam arrangement is highly sensitive to motion (diffusion) of the spin carriers within the illuminated volume and thus can provide additional information about spin dynamics and spatial correlations of spin polarization in volume media. Our quantitative estimates show that, under real experimental conditions, spin diffusion may strongly suppress the spin-noise signal in the two-beam geometry. Mechanism of this suppression is similar to that of the time-of-flight broadening with the critical distance determined by the period of spatial interference of the two beams rather than by the beam diameter.