Dynamics of a Fermi gas quenched to unitarity

TL;DR

This study experimentally investigates how a two-component Fermi gas evolves after a rapid change to unitarity, revealing different timescales for pair formation, condensation, and short-range correlations.

Contribution

It provides detailed measurements of the dynamics of pair formation and condensation in a Fermi gas following an interaction quench to unitarity, highlighting the different evolution timescales.

Findings

Contact parameter responds rapidly to interaction changes.

Pair formation and condensation occur on different timescales.

Short-range correlations evolve faster than low-momentum pair condensation.

Abstract

We present an experimental study of a two component Fermi gas following an interaction quench into the superfluid phase. Starting with a weakly attractive gas in the normal phase, interactions are ramped to unitarity at a range of rates and we measure the subsequent dynamics as the gas approaches equilibrium. Both the formation and condensation of fermion pairs are mapped via measurements of the pair momentum distribution and can take place on very different timescales, depending on the adiabaticity of the quench. The contact parameter is seen to respond very quickly to changes in the interaction strength, indicating that short-range correlations, based on the occupation of high-momentum modes, evolve far more rapidly than the correlations in low-momentum modes necessary for pair condensation.