Realization of a strongly interacting Bose-Fermi mixture from a two-component Fermi gas

TL;DR

This paper demonstrates how a two-component Fermi gas with population imbalance can form a strongly interacting Bose-Fermi mixture, revealing the composite nature of bosons immersed in a Fermi sea through in situ density profile analysis.

Contribution

It identifies the critical interaction strength for pairing and characterizes scattering lengths and beyond-mean-field effects in the mixture.

Findings

All minority atoms pair with majority atoms beyond a critical interaction.

The system behaves as a boson-fermion mixture in the strongly interacting regime.

Determined dimer-fermion and dimer-dimer scattering lengths.

Abstract

We show the emergence of a strongly interacting Bose-Fermi mixture from a two-component Fermi mixture with population imbalance. By analyzing in situ density profiles of $^6$Li atoms in the BCS-BEC crossover regime we identify a critical interaction strength, beyond which all minority atoms pair up with majority atoms, and form a Bose condensate. This is the regime where the system can be effectively described as a boson-fermion mixture. We determine the dimer-fermion and dimer-dimer scattering lengths and beyond-mean-field contributions. Our study realizes a Gedanken experiment of bosons immersed in a Fermi sea of one of their constituents, revealing the composite nature of the bosons.