Universal behavior of pair correlations in a strongly interacting Fermi gas

TL;DR

This paper demonstrates that short-range pair correlations in a strongly interacting Fermi gas follow a universal law described by Tan's relations, confirmed through Bragg spectroscopy measurements across various momenta and interaction strengths.

Contribution

The study provides experimental validation of the universal behavior of pair correlations in a Fermi gas using Bragg spectroscopy and Tan's relations.

Findings

Structure factor scales as C/q, confirming universality.

Bragg spectroscopy accurately measures pair correlations.

Calibration with the f-sum rule improves measurement precision.

Abstract

We show that short-range pair correlations in a strongly interacting Fermi gas follow a simple universal law described by Tan's relations. This is achieved through measurements of the static structure factor which displays a universal scaling proportional to the ratio of Tan's contact to the momentum $C/q$. Bragg spectroscopy of ultracold $^6$Li atoms from a periodic optical potential is used to measure the structure factor for a wide range of momenta and interaction strengths, providing broad confirmation of this universal law. We calibrate our Bragg spectra using the $f$-sum rule, which is found to improve the accuracy of the structure factor measurement.