# Effect of boson on-site repulsion on the superfluidity in the boson-fermion-Hubbard model

## TL;DR

This paper investigates how boson on-site repulsion influences superfluidity in a boson-fermion-Hubbard model, revealing conditions for resonant superfluid phases and temperature enhancements via Feshbach interactions.

## Contribution

It introduces a detailed analysis of the phase diagram considering Feshbach interactions and bosonic band positions, highlighting the emergence of resonant superfluid phases under specific conditions.

## Key findings

- Resonant superfluid phase can exist for any fermion concentration near integer boson filling.
- Feshbach interaction can significantly enhance the critical temperature of superfluidity.
- Standard time-of-flight experiments can detect the resonant superfluid phase.

## Abstract

We analyze the finite-temperature phase diagram of the boson-fermion-Hubbard model with Feshbach converting interaction, using the coherent-state path-integral method. We show that depending on the position of the bosonic band, this type of interaction, even if weak, can drive the system into the resonant superfluid phase in the strong bosonic interaction limit. It turns out that this phase can exist for an arbitrary number of fermions (i.e., fermionic concentration between 0 and 2) but with the bosonic particle number very close to an integer value. We point out that the standard time-of-flight method in optical lattice experiments can be an adequate technique to confirm the existence of this resonant phase. Moreover, in the non-resonant regime, the enhancement of the critical temperature of the superfluid phase due to Feshbach interaction is also observed. We account for this interesting phenomena for a hole- or particlelike pairing mechanism depending on the system density and mutual location of the fermionic and bosonic bands.