Contact interaction in an unitary ultracold Fermi gas

TL;DR

This paper introduces a quantum Monte Carlo method to accurately simulate ultracold Fermi gases at unitarity with true contact interactions, achieving results that align well with experimental data and enabling more precise future studies.

Contribution

It presents the first quantum Monte Carlo approach handling true contact interactions in ultracold Fermi gases, improving accuracy and variance control.

Findings

Results agree with experimental Bertsch and contact parameters.

Method reduces variance in Monte Carlo calculations.

Enables more faithful modeling of ultracold atomic gases.

Abstract

An ultracold Fermi atomic gas at unitarity presents universal properties that in the diluted limit can be well described by a contact interaction. By employing a guide function with correct boundary conditions and making simple modifications to the sampling procedure we are able to handle for the first time a true contact interaction in a quantum Monte Carlo calculation. The results are obtained with small variances. Our calculations for the Bertsch and contact parameters are in excellent agreement with published experiments. The possibility of using a more faithfully description of ultracold atomic gases can help uncover features yet unknown of the ultracold atomic gases. In addition, this work paves the way to perform quantum Monte Carlo calculations for systems interacting with contact interactions, where in many cases the description using potentials with finite effective range might not be accurate.