Condensation of Pairs of Fermionic Atoms Near a Feshbach Resonance

TL;DR

This paper reports the observation of Bose-Einstein condensation of fermionic atom pairs in ultracold ^6Li gas near a Feshbach resonance, revealing high condensate fractions and the existence of quasi-stable molecules above the resonance.

Contribution

It provides the first experimental evidence of fermionic atom pair condensation above a Feshbach resonance and accurately determines the resonance position.

Findings

Condensate fractions up to 80% were achieved.

Pairs of fermionic atoms form quasi-stable molecules above the resonance.

The resonance position was precisely measured at 822±3 G.

Abstract

We have observed Bose-Einstein condensation of pairs of fermionic atoms in an ultracold ^6Li gas at magnetic fields above a Feshbach resonance, where no stable ^6Li_2 molecules would exist in vacuum. We accurately determined the position of the resonance to be 822+-3 G. Molecular Bose-Einstein condensates were detected after a fast magnetic field ramp, which transferred pairs of atoms at close distances into bound molecules. Condensate fractions as high as 80% were obtained. The large condensate fractions are interpreted in terms of pre-existing molecules which are quasi-stable even above the two-body Feshbach resonance due to the presence of the degenerate Fermi gas.