Berezinskii-Kosterlitz-Thouless transition in the time-reversal-symmetric Hofstadter-Hubbard model

TL;DR

This paper investigates the Berezinskii-Kosterlitz-Thouless transition in a time-reversal-symmetric Hofstadter-Hubbard model, revealing how inter-band effects dominate phase stiffness as interactions increase in a two-component Fermi gas system.

Contribution

It introduces a self-consistent BCS-BKT approach that explicitly considers the multi-band butterfly spectrum, highlighting the dominance of inter-band contributions to phase stiffness.

Findings

Inter-band contributions to phase stiffness increase with interaction strength.

The BKT transition temperature is affected by the magnetic flux and interaction parameters.

Multi-band effects are crucial for understanding superfluid properties in this model.

Abstract

Assuming that two-component Fermi gases with opposite artificial magnetic fields on a square optical lattice are well-described by the so-called time-reversal-symmetric Hofstadter-Hubbard model, we explore the thermal superfluid properties along with the critical Berezinskii-Kosterlitz-Thouless (BKT) transition temperature in this model over a wide-range of its parameters. In particular, since our self-consistent BCS-BKT approach takes the multi-band butterfly spectrum explicitly into account, it unveils how dramatically the inter-band contribution to the phase stiffness dominates the intra-band one with an increasing interaction strength for any given magnetic flux.