Cross-correlation spin noise spectroscopy of heterogeneous interacting spin systems

TL;DR

This paper introduces a minimally invasive method using cross-correlation spin noise spectroscopy to characterize interactions in heterogeneous spin systems, confirmed experimentally with alkali vapors, revealing spin exchange and relaxation dynamics.

Contribution

It presents a novel approach for probing inter-species spin interactions through cross-correlation spin noise spectroscopy in thermal equilibrium.

Findings

Successful experimental validation with Rb and Cs vapors

Quantitative insights into spin exchange rates

Observation of spin relaxation under equilibrium conditions

Abstract

We develop and apply a minimally invasive approach for characterization of inter-species spin interactions by detecting spin fluctuations alone. We consider a heterogeneous two-component spin ensemble in thermal equilibrium that interacts via binary exchange coupling, and we determine cross-correlations between the intrinsic spin fluctuations exhibited by the two species. Our theoretical predictions are experimentally confirmed using `two-color' optical spin noise spectroscopy on a mixture of interacting Rb and Cs alkali vapors. The results allow us to explore the rates of spin exchange and total spin relaxation under conditions of strict thermodynamic equilibrium.