Measurement of interaction energy near a Feshbach resonance in a 6Li Fermi gas

TL;DR

This study measures the interaction energy near a Feshbach resonance in a $^6$Li Fermi gas, revealing a significant shift between the resonance and atom loss features, with implications for understanding strongly interacting quantum gases.

Contribution

First precise measurement of the Feshbach resonance position in a $^6$Li Fermi gas near 800 G, including observation of an unexpected large shift in resonance features.

Findings

Resonance at 800(40) G matches theoretical predictions.

Anisotropic expansion explained by collisional hydrodynamics.

Large 80 G shift observed between resonance peak and atom loss maximum.

Abstract

We investigate the strongly interacting regime in an optically trapped $^6$Li Fermi mixture near a Feshbach resonance. The resonance is found at $800(40) $G in good agreement with theory. Anisotropic expansion of the gas is interpreted by collisional hydrodynamics. We observe an unexpected and large shift ($80 $G) between the resonance peak and both the maximum of atom loss and the change of sign of the interaction energy.