Measurement of the Zero Crossing in a Feshbach Resonance of Fermionic 6-Li

TL;DR

This paper experimentally measures a zero crossing in the scattering length of fermionic 6-Li near 528 G and predicts additional Feshbach resonances, aiding control of interactions in ultracold fermionic gases.

Contribution

It provides the first precise experimental measurement of the zero crossing in 6-Li and offers theoretical predictions of additional resonances.

Findings

Zero crossing at 528 G with minimal evaporation effects

Broad Feshbach resonance around 860 G confirmed

Predicted narrow resonance near 550 G

Abstract

We measure a zero crossing in the scattering length of a mixture of the two lowest hyperfine states of 6-Li. To locate the zero crossing, we monitor the decrease in temperature and atom number arising from evaporation in a CO2 laser trap as a function of magnetic field B. The temperature decrease and atom loss are minimized for B=528(4) G, consistent with no evaporation. We also present preliminary calculations using potentials that have been constrained by the measured zero crossing and locate a broad Feshbach resonance at approximately 860 G, in agreement with previous theoretical predictions. In addition, our theoretical model predicts a second and much narrower Feshbach resonance near 550 G.