Probing the Interface of a Phase-Separated State in a Repulsive Bose-Fermi Mixture

TL;DR

This study investigates the interface in a phase-separated Bose-Fermi mixture, revealing how interspecies repulsion and kinetic energy influence the interface's properties and the phase transition's nature.

Contribution

It provides experimental measurements and theoretical insights into the interface structure and phase transition smoothing in a Bose-Fermi mixture with tunable interactions.

Findings

Residual spatial overlap measured via three-body losses.

Kinetic energy term is crucial for maintaining a thin interface.

Finite size effects lead to smoothing of the phase transition.

Abstract

We probe the interface between a phase-separated Bose-Fermi mixture consisting of a small BEC of $^{41}$K residing in a large Fermi sea of $^6$Li. We quantify the residual spatial overlap between the two components by measuring three-body recombination losses for variable strength of the interspecies repulsion. A comparison with a numerical mean-field model highlights the importance of the kinetic energy term for the condensed bosons in maintaining the thin interface far into the phase-separated regime. Our results demonstrate a corresponding smoothing of the phase transition in a system of finite size.