Long-range interactions revealed by collective spin noise spectra in atomic vapors

TL;DR

This paper uncovers long-range dipole-dipole interactions in dense atomic vapors through anomalous features in spin noise spectra, revealing many-body effects and correlations beyond traditional models.

Contribution

It demonstrates that spin noise spectroscopy can detect many-body interactions and correlations in dense atomic vapors, advancing the understanding of collective spin dynamics.

Findings

Observation of spectral broadening at high densities

Detection of an unexpected low-frequency noise component

Evidence of strong long-range dipole-dipole interactions

Abstract

We report anomalous features in the spin noise spectroscopy (SNS) of a thin cell of a dense vapor of alkali atoms. At high densities and close to resonance, we observe a dramatic broadening of the spin noise spectra as well as an unexpected extra low-frequency noise component. With the help of a two-body model and simulations, we show that these features are the hallmark of a strong, long-range dipole-dipole interaction within the ensemble. The additional low-frequency noise reveals the correlated evolution of pair of atoms beyond the impact approximation. In this regime, we demonstrate that spin noise can no longer be obtained from one-body dynamics, opening the way for the characterization of many-body spin noise, atomic entanglement or higher order spin correlators in atomic vapors using SNS.