Spin noise of localized electrons interacting with optically cooled nuclei

TL;DR

This paper develops a microscopic theory describing how localized electron spin noise spectra are influenced by optically cooled nuclear spins, revealing effects of nuclear polarization and external magnetic fields on spin fluctuations.

Contribution

It introduces a new theoretical framework for understanding electron spin noise affected by nuclear spin cooling and polarization, highlighting the impact of magnetic fields and nuclear temperature.

Findings

Nuclear spin polarization affects electron spin fluctuations similarly to external magnetic fields.

High nuclear polarization suppresses hyperfine fluctuations and narrows spin noise peaks.

The theory suggests experimental methods to probe nuclear spin systems via spin noise spectroscopy.

Abstract

A microscopic theory of spin fluctuations of localized electrons interacting with optically cooled nuclear spin bath has been developed. Since nuclear spin temperature may stay low enough for macroscopically long time, the nuclear spin system becomes very sensitive to an external magnetic field. This strongly affects electron spin noise spectrum. It has been shown that in the case of weak fields/relatively high nuclear spin temperature, a small degree of nuclear spin polarization affect the electron spin fluctuations in the same way as an additional external magnetic field. By contrast, the high degree of nuclear polarization realized in relatively strong magnetic field and low nuclear spin temperature leads to a suppression of hyperfine field fluctuations and to a dramatic narrowing of precession-induced peak in the spin noise spectrum. The experimental possibilities of nuclear spin system investigation by means of spin noise spectroscopy are discussed.