The neutron polaron as a constraint on nuclear density functionals

TL;DR

This paper investigates the energy of a neutron polaron in strongly interacting fermionic systems, using Quantum Monte Carlo and effective field theory, revealing discrepancies in nuclear density functionals and providing constraints for improvement.

Contribution

It maps the neutron polaron problem to nuclear physics, presents new Quantum Monte Carlo results, and highlights the need to refine nuclear density functionals based on these findings.

Findings

State-of-the-art nuclear density functionals underestimate neutron polaron energy.

Quantum Monte Carlo results provide new benchmarks.

Constraints are proposed for improving nuclear density functionals.

Abstract

We study the energy of an impurity (polaron) that interacts strongly in a sea of fermions when the effective range of the impurity-fermion interaction becomes important, thereby mapping the Fermi polaron of condensed matter physics and ultracold atoms to strongly interacting neutrons. We present Quantum Monte Carlo results for this neutron polaron, and compare these with effective field theory calculations that also include contributions beyond the effective range. We show that state-of-the-art nuclear density functionals vary substantially and generally underestimate the neutron polaron energy. Our results thus provide constraints for adjusting the time-odd components of nuclear density functionals to better characterize polarized systems.