High-Temperature Atomic Superfluidity in Lattice Boson-Fermion Mixtures

TL;DR

This paper investigates superfluidity in lattice boson-fermion mixtures, demonstrating that boson-fermion interactions can induce attractive fermion pairing and enhance superfluidity even with repulsive fermion interactions.

Contribution

It proves that boson-fermion interactions always induce attractive fermion-fermion coupling under certain conditions and predicts an enhanced BEC-BCS crossover in optical lattices.

Findings

Induced fermion-fermion attraction is always attractive with repulsive boson-boson interactions.

Enhanced BEC-BCS crossover occurs as lattice potential varies.

Superfluidity can arise from induced attraction even with direct fermion repulsion.

Abstract

We consider atomic Bose-Fermi mixtures in optical lattices and study the superfluidity of fermionic atoms due to s-wave pairing induced by boson-fermion interactions. We prove that the induced fermion-fermion coupling is always {\it attractive} if the boson-boson on site interaction is repulsive, and predict the existence of an enhanced BEC--BCS crossover as the strength of the lattice potential is varied. We show that for direct on-site fermion-fermion {\it repulsion}, the induced attraction can give rise to superfluidity via s-wave pairing, at striking variance with the case of pure systems of fermionic atoms with direct repulsive interactions.