Observation of pair condensation in the quasi-2D BEC-BCS crossover

TL;DR

This study demonstrates the formation of a fermion pair condensate in a quasi-2D ultracold Fermi gas, providing insights into superfluidity mechanisms in reduced dimensions through in situ measurements and phase diagram mapping.

Contribution

It introduces a novel in situ measurement technique to observe pair condensation and maps the phase diagram of the quasi-2D BEC-BCS crossover.

Findings

Observation of low-momentum fermion pair condensate at low temperatures

Mapping of the phase diagram across the BEC-BCS crossover

Demonstration of pairing mechanisms in reduced-dimensional systems

Abstract

The condensation of fermion pairs lies at the heart of superfluidity. However, for strongly correlated systems with reduced dimensionality the mechanisms of pairing and condensation are still not fully understood. In our experiment we use ultracold atoms as a generic model system to study the phase transition from a normal to a condensed phase in a strongly interacting quasi-two-dimensional Fermi gas. Using a novel method, we obtain the in situ pair momentum distribution of the strongly interacting system and observe the emergence of a low-momentum condensate at low temperatures. By tuning temperature and interaction strength we map out the phase diagram of the quasi-2D BEC-BCS crossover.