Nonlinear spectroscopy of high-spin fluctuations

TL;DR

This paper explores how high-spin fluctuations exhibit nonlinear behavior in spin noise spectra under strong electromagnetic fields, revealing effects like high harmonics and sensitivity to field orientation, advancing understanding of spin dynamics.

Contribution

It provides both theoretical predictions and experimental validation of nonlinear spin noise effects in high-spin systems, highlighting new phenomena beyond linear response.

Findings

Spin noise spectra are highly sensitive to probe polarization and magnetic field orientation.

High harmonics of the Larmor frequency appear in the noise spectra.

Strong electromagnetic fields cause renormalization of spin states, affecting noise characteristics.

Abstract

We investigate theoretically and experimentally fluctuations of high spin (F>1/2) beyond the linear response regime and demonstrate dramatic modifications of the spin noise spectra in the high power density probe field. Several effects related to an interplay of high spin and perturbation are predicted theoretically and revealed experimentally, including strong sensitivity of the spin noise spectra to the mutual orientation of the probe polarization plane and magnetic field direction, appearance of high harmonics of the Larmor frequency in the spin noise and the fine structure of the Larmor peaks. We demonstrate the ability of the spin-noise spectroscopy to access the nonlinear effects related to the renormalization of the spin states by strong electromagnetic fields.