Exact Numerical Study of Pair Formation with Imbalanced Fermion Populations

TL;DR

This study uses exact Quantum Monte Carlo methods to analyze pair formation in an imbalanced fermion population within a 1D Hubbard model, revealing FFLO phase characteristics and effects of confinement.

Contribution

First exact numerical analysis demonstrating FFLO phase features and momentum distributions in imbalanced fermion systems with confinement effects.

Findings

Pair-pair correlations develop oscillations with polarization.

Pair momentum peaks at Fermi momentum difference.

FFLO oscillations persist under trapping potential.

Abstract

We present an exact Quantum Monte Carlo study of the attractive 1-dimensional Hubbard model with imbalanced fermion population. The pair-pair correlation function, which decays monotonically in the absence of polarization P, develops oscillations when P is nonzero, characteristic of Fulde-Ferrell-Larkin-Ovchinnikov phase. The pair momentum distribution peaks at a momentum equal to the difference in the Fermi momenta. At strong coupling, the minority and majority momentum distributions are shown to be deformed, reflecting the presence of the other species, and its Fermi surface. The FFLO oscillations survive the presence of a confining potential, and the local polarization at the trap center exhibits a marked dip, similar to that observed experimentally.