Evolution from BCS to BKT superfluidity in one-dimensional optical lattices

TL;DR

This paper investigates the evolution of superfluid phases in one-dimensional optical lattices, showing a transition from BCS to BKT superfluidity with increasing interaction strength, and characterizes vortex excitations across this crossover.

Contribution

It provides a detailed analysis of the finite temperature phase diagram and identifies the dimensional crossover from 3D to 2D superfluidity in fermion mixtures.

Findings

Critical temperature varies with interaction strength.

Dimensional crossover occurs at specific interaction regimes.

Vortex excitations change from elliptical loops to vortex-antivortex pairs.

Abstract

We analyze the finite temperature phase diagram of fermion mixtures in one-dimensional optical lattices as a function of interaction strength. At low temperatures, the system evolves from an anisotropic three-dimensional Bardeen-Cooper-Schrieffer (BCS) superfluid to an effectively two-dimensional Berezinskii-Kosterlitz-Thouless (BKT) superfluid as the interaction strength increases. We calculate the critical temperature as a function of interaction strength, and identify the region where the dimensional crossover occurs for a specified optical lattice potential. Finally, we show that the dominant vortex excitations near the critical temperature evolve from multiplane elliptical vortex loops in the three-dimensional regime to planar vortex-antivortex pairs in the two-dimensional regime, and we propose a detection scheme for these excitations.