Diffusion Monte Carlo study of a spin-imbalanced two-dimensional Fermi gas with attractive interactions

TL;DR

This study uses Diffusion Monte Carlo to investigate the superconducting properties of a spin-imbalanced 2D Fermi gas with attractive interactions, revealing non-uniform pairing beyond traditional FFLO theory.

Contribution

It demonstrates the presence of nonzero pair momentum condensate fractions, extending understanding of pairing mechanisms in spin-imbalanced Fermi gases.

Findings

Nonzero condensate fraction at finite pair momentum

Evidence of spatially non-uniform superconducting order

Extension beyond FFLO pairing theory

Abstract

We probe the superconducting gap in the zero temperature ground state of an attractively interacting spin-imbalanced two-dimensional Fermi gas with Diffusion Monte Carlo. A condensate fraction at nonzero pair momentum evidences a spatially non-uniform superconducting order parameter. Comparison with exact diagonalisation studies confirms that the nonzero condensate fraction across a range of nonzero fermion pair momenta is consistent with non-exclusive pairing between majority and minority fermions, an extension beyond FFLO theory.