Bragg spectroscopy of a strongly interacting Fermi gas

TL;DR

This paper uses Bragg spectroscopy to explore the BEC-BCS crossover in a strongly interacting Fermi gas, revealing pairing signatures and characterizing two-body correlations across a Feshbach resonance.

Contribution

It provides the first detailed Bragg spectroscopy measurements of the dynamic and static structure factors during the BEC-BCS crossover in a fermionic gas.

Findings

Observed a smooth spectral transition from molecular to atomic states.

Detected clear signatures of pairing at and above unitarity.

Measured the density dependence of two-body correlations.

Abstract

We present a comprehensive study of the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover in fermionic $^6$Li using Bragg spectroscopy. A smooth transition from molecular to atomic spectra is observed with a clear signature of pairing at and above unitarity. These spectra probe the dynamic and static structure factors of the gas and provide a direct link to two-body correlations. We have characterised these correlations and measured their density dependence across the broad Feshbach resonance at 834 G.