Spin 1/2 Fermions in the Unitary Regime: A Superfluid of a New Type

TL;DR

This paper investigates a dilute system of spin 1/2 fermions at unitarity, revealing a novel superfluid phase with mixed fermionic and bosonic features through non-perturbative calculations of thermodynamics and phase transition properties.

Contribution

It provides the first comprehensive non-perturbative analysis of thermodynamic properties and superfluid transition in a unitary Fermi gas, identifying a new superfluid type with unique characteristics.

Findings

Thermodynamic properties show mixed fermionic and bosonic features.

Critical temperature for superfluid transition determined.

Identification of a new superfluid phase with unique thermal response.

Abstract

We have studied, in a fully non-perturbative calculation, a dilute system of spin 1/2 interacting fermions, characterized by an infinite scattering length at finite temperatures. Various thermodynamic properties and the condensate fraction were calculated and we have also determined the critical temperature for the superfluid-normal phase transition in this regime. The thermodynamic behavior appears as a rather surprising and unexpected melange of fermionic and bosonic features. The thermal response of a spin 1/2 fermion at the BCS-BEC crossover should be classified as that of a new type of superfluid.