Numerical study of unitary fermions in one spatial dimension

TL;DR

This study uses lattice Monte Carlo methods to analyze universal properties of four-component fermions in one dimension, providing precise energy and contact density measurements for few- and many-body systems, and verifying theoretical relations.

Contribution

It presents the first comprehensive lattice Monte Carlo analysis of one-dimensional four-component fermions, including continuum extrapolations and verification of virial theorems.

Findings

Agreement with exact energies for small systems within 1%

Universal quantities like the Bertsch parameter are estimated with high precision

Virial theorems are confirmed for trapped and untrapped systems

Abstract

I perform lattice Monte Carlo studies of universal four-component fermion systems in one spatial dimension. Continuum few-body observables (i.e., ground-state energies and integrated contact densities) are determined for both unpolarized and polarized systems of up to eight fermions confined to a harmonic trap. Estimates of the continuum energies for four and five trapped fermions show agreement with exact analytic calculations to within approximately one percent statistical uncertainties. Continuum many-body observables are determined for unpolarized systems of up to 88 fermions confined to a finite box, and 56 fermions confined to a harmonic trap. Results are reported for universal quantities such as the Bertsch parameter, defined as the energy of the untrapped many-body system in units of the corresponding free-gas energy, and its subleading correction at large but finite scattering length. Two independent estimates of these quantities are obtained from thermodynamic limit extrapolations of continuum extrapolated observables. A third estimate of the Bertsch parameter is obtained by combining estimates of the untrapped and trapped integrated contact densities with additional theoretical input from a calculation based on Thomas-Fermi theory. All estimates of the Bertsch parameter and its subleading correction are found to be consistent to within approximately one percent statistical uncertainties. Finally, the continuum restoration of virial theorems is verified for both few- and many-body systems confined to a trap.