From the Cooper problem to canted supersolids in Bose-Fermi mixtures

TL;DR

This paper explores the phase diagram of a 3D Bose-Fermi Hubbard model, revealing various superfluid, supersolid, and charge density wave phases influenced by boson speed and interspecies interactions, with implications for cold gas experiments.

Contribution

It provides the first detailed phase diagram of the 3D Bose-Fermi Hubbard model using dynamical mean-field theory, highlighting novel phases like canted supersolids.

Findings

Fast bosons induce s-wave pairing in fermions.

Multiple phases including superfluid, supersolid, and charge density wave are identified.

Phase diagram accessible to cold gas experiments.

Abstract

We calculate the phase diagram of the Bose-Fermi Hubbard model on the 3d cubic lattice at fermionic half filling and bosonic unit filling by means of single-site dynamical mean-field theory. For fast bosons, this is equivalent to the Cooper problem in which the bosons can induce s-wave pairing between the fermions. We also find miscible superfluid and canted supersolid phases depending on the interspecies coupling strength. In contrast, slow bosons favor fermionic charge density wave structures for attractive fermionic interactions. These competing instabilities lead to a rich phase diagram within reach of cold gas experiments.