Superfuid-insulator transitions at non-integer filling in optical lattices of fermionic atoms

TL;DR

This paper explores superfluid-insulator transitions in fermionic atoms within optical lattices, revealing new insulating phases at non-integer fillings caused by pair localization and strong interactions, with implications for experimental detection.

Contribution

It identifies novel insulating phases at non-integer fillings in the attractive Hubbard model, driven by pair localization and strong interactions, expanding understanding beyond traditional band and Mott insulators.

Findings

New insulating phases at non-integer fillings due to pair localization.

Superfluid transition temperatures and ground states characterized.

Potential experimental detection via fermionic optical lattices.

Abstract

We determine the superfluid transition temperatures $T_c$ and the ground states of the attractive Hubbard model and find new insulating phases associated with non-integer filling at sufficiently strong pairing attraction $|U|$. These states, distinct from band and Mott insulating phases, derive from pair localization; pair hopping at large $|U|$ and high densities is impeded by inter-site, inter-pair repulsive interactions. The best way to detect the breakdown of superfluidity is using fermionic optical lattices which should reveal new forms of ``bosonic'' order, reflecting ground state pairing without condensation.