From resonantly interacting fermions with effective range to neutron matter

TL;DR

This paper introduces a density functional theory for strongly interacting fermions with large negative scattering length, accurately modeling unitary gases and neutron matter, incorporating effective range effects, and matching recent quantum Monte-Carlo results.

Contribution

The paper develops a two-parameter density functional that captures universal properties of unitary fermions and extends to include effective range effects, improving modeling of neutron matter.

Findings

Functional reproduces experimental data at unitarity and away from it

Accurately predicts Tan's contact parameter with effective range effects

Matches recent quantum Monte-Carlo results for neutron matter

Abstract

A density functional theory is proposed for strongly interacting fermions with arbitrary large negative scattering length. The functional has only two parameters that are directly fixed to reproduce the universal properties of unitary gas: the so-called "Bertsch parameter" $\xi_0$ and a parameter $\eta_e$ related to the possible influence of the effective range $r_e$ at infinite scattering length $a$. Using most recent quantum Monte-Carlo (QMC) estimates of these two parameters, it is shown that the functional properly reproduces the experimental measurements of interacting Fermi systems not only at unitarity but also away from this limit over a wide range of $(ak_F)^{-1}$ values. The functional is applied to obtain an expression of the Tan's contact parameter including the effect of $r_e$. Application is finally made to neutron matter. It is shown that most recent QMC results are well reproduced.