Hydrodynamic Expansion of a Strongly Interacting Fermi-Fermi Mixture

TL;DR

This paper investigates the hydrodynamic expansion behaviors of a strongly interacting Fermi-Fermi mixture of Li-6 and K-40 atoms, revealing aspect ratio inversion and collective joint expansion phenomena near a Feshbach resonance.

Contribution

It presents the first experimental observation of collective expansion where different atomic species expand together, advancing understanding of many-body physics in Fermi mixtures.

Findings

Observation of aspect ratio inversion during expansion

Detection of collective joint expansion of different species

Insights into strongly interacting Fermi-Fermi systems

Abstract

We report on the expansion of a Fermi-Fermi mixture of Li-6 and K-40 atoms under conditions of strong interactions realized near the center of an interspecies Feshbach resonance. We observe two different phenomena of hydrodynamic behavior. The first one is the well-known inversion of the aspect ratio. The second one is a collective expansion, where both species stick together and despite of their different masses expand jointly. Our work constitutes a first step to explore the intriguing many-body physics of this novel system.