Inelastic Collisions of a Fermi Gas in the BEC-BCS Crossover

TL;DR

This study measures inelastic collision rates in a Fermi gas near the BEC-BCS crossover, revealing suppression effects and the coexistence of two- and three-body decay processes influenced by temperature and magnetic field.

Contribution

It provides the first detailed measurements of inelastic decay rates in a Fermi gas across the BEC-BCS crossover, highlighting the role of Pauli exclusion and pairing effects.

Findings

Three-body decay dominates at high temperature.

Two-body decay becomes significant near and below resonance.

Decay mechanisms involve molecules and Cooper pairs.

Abstract

We report the measurement of inelastic three-body and two-body collisional decay rates for a two-component Fermi gas of $^6$Li, which are highly suppressed by the Pauli exclusion principle. Our measurements are made in the BEC-BCS crossover regime, near the two-body collisional (Feshbach) resonance. At high temperature (energy) the data shows a dominant three-body decay process, which is studied as a function of bias magnetic field. At low energy, the data shows a coexistence of two-body and three-body decay processes near and below the Feshbach resonance. Below resonance, the observed two-body inelastic decay can arise from molecule-atom and molecule-molecule collisions. We suggest that at and above resonance, an effective two-body decay rate arises from collisions between atoms and correlated (Cooper) pairs that can exist at sufficiently low temperature.