Density-induced BCS to Bose-Einstein crossover

TL;DR

This paper explores how particle density influences the BCS to Bose-Einstein crossover at zero temperature, analyzing different potentials and pairing symmetries in continuum and lattice models, revealing complex correlation effects.

Contribution

It provides a detailed mean-field analysis of the density-driven BCS-BEC crossover, including the effects of various potentials and pairing symmetries, and uncovers novel correlation phenomena near half filling.

Findings

Density significantly affects the crossover behavior.

Strong correlations lead to antiferromagnetic order near half filling.

Different potentials and pairing symmetries exhibit distinct crossover characteristics.

Abstract

We investigate the zero-temperature BCS to Bose-Einstein crossover at the mean-field level, by driving it with the attractive potential and the particle density.We emphasize specifically the role played by the particle density in this crossover.Three different interparticle potentials are considered for the continuum model in three spatial dimensions, while both s- and d-wave solutions are analyzed for the attractive (extended) Hubbard model on a two-dimensional square lattice. For this model the peculiar behavior of the crossover for the d-wave solution is discussed.In particular, in the strong-coupling limit when approaching half filling we evidence the occurrence of strong correlations among antiparallel-spin fermions belonging to different composite bosons, which give rise to a quasi-long-range antiferromagnetic order in this limit.