Observation of resonance condensation of fermionic atom pairs

TL;DR

This paper reports the experimental observation of fermionic atom pair condensation in the BCS-BEC crossover regime using ultracold 40K atoms, with precise control and measurement techniques to explore the transition.

Contribution

It introduces a novel pairing projection technique to measure fermionic atom pair momentum distributions across the BCS-BEC crossover.

Findings

Observation of fermionic pair condensation.

Mapping of the transition as a function of temperature and magnetic field.

Precise determination of the Feshbach resonance location.

Abstract

We have observed condensation of fermionic atom pairs in the BCS-BEC crossover regime. A trapped gas of fermionic 40K atoms is evaporatively cooled to quantum degeneracy and then a magnetic-field Feshbach resonance is used to control the atom-atom interactions. The location of this resonance is precisely determined from low-density measurements of molecule dissociation. In order to search for condensation on either side of the resonance we introduce a technique that pairwise projects fermionic atoms onto molecules; this enables us to measure the momentum distribution of fermionic atom pairs. The transition to condensation of fermionic atom pairs is mapped out as a function of the initial atom gas temperature T compared to the Fermi temperature TF for magnetic-field detunings on both the BCS and BEC sides of the resonance.