Quantum Monte Carlo study of dilute neutron matter at finite temperatures

TL;DR

This paper uses Path Integral Monte Carlo methods to study dilute neutron matter at finite temperatures, revealing superfluid transition properties and quasiparticle spectra with implications for nuclear physics.

Contribution

It provides the first non-perturbative PIMC calculations of dilute neutron matter including spectral functions and superfluid transition analysis.

Findings

Estimated critical temperature for superfluid transition.

Determined quasiparticle effective mass, potential, and gap.

Found large gap-to-critical temperature ratio indicating non-BCS superfluidity.

Abstract

We report results of fully non-perturbative, Path Integral Monte Carlo (PIMC) calculations for dilute neutron matter. The neutron-neutron interaction in the s channel is parameterized by the scattering length and the effective range. We calculate the energy and the chemical potential as a function of temperature at the density $\dens=0.003\fm^{-3}$. The critical temperature $\Tc$ for the superfluid-normal phase transition is estimated from the finite size scaling of the condensate fraction. At low temperatures we extract the spectral weight function $A(p,\omega)$ from the imaginary time propagator using the methods of maximum entropy and singular value decomposition. We determine the quasiparticle spectrum, which can be accurately parameterized by three parameters: an effective mass $m^*$, a mean-field potential $U$, and a gap $\Delta$. Large value of $\Delta/\Tc$ indicates that the system is not a BCS-type superfluid at low temperatures.