Pairing between Atoms and Molecules in a Boson-Fermion Resonant Mixture

TL;DR

This paper investigates atom-molecule pairing in a boson-fermion mixture near Feshbach resonances, revealing coexistence of heteronuclear molecules and fermionic atoms, and exploring the potential for exotic pairing states like FFLO.

Contribution

It provides a detailed analysis of pairing mechanisms and the conditions for atom-molecule pair formation in boson-fermion mixtures near Feshbach resonances, including the possibility of realizing FFLO states.

Findings

Heteronuclear molecules coexist with fermionic atoms over a wide parameter range.

Attraction between atoms and molecules can lead to atom-molecule pairing.

Potential realization of FFLO state in the mixture.

Abstract

We consider a mixture of fermionic and bosonic atoms nearby interspecies Feshbach resonances, which have been observed recently in $^6$Li-$^{23}$Na mixture by MIT group, and in $^{40}$K-$^{87}$Rb mixture by JILA group. We point out that the fermion-boson bound state, namely the heteronuclear molecules, will coexist with the fermionic atoms in a wide parameter region, and the attraction between fermionic atoms and molecules will lead to the formation of atom-molecule pairs. The pairing structure is studied in detail, and, in particular, we highlight the possible realization of the Fulde-Ferrel-Larkin-Ovchinnikov state in this system.