Supercurrent Flow in NJL_{2+1} at High Baryon Density

TL;DR

This paper uses numerical simulations of the 2+1d NJL model at high baryon density to investigate supercurrent flow and superfluid properties, including the helicity modulus and critical temperature.

Contribution

It introduces a novel method to measure the helicity modulus in the NJL model by varying the diquark source phase smoothly across the lattice.

Findings

Non-zero supercurrent persists as source strength approaches zero.

Estimated critical temperature aligns with vortex-unbinding transition in thin-film superfluids.

Helicity modulus provides a quantitative measure of superfluid stiffness.

Abstract

We present results of numerical simulations of the 2+1d Nambu -- Jona-Lasinio model with non-zero baryon chemical potential mu and spatially-varying complex diquark source strength j. By choosing arg(j) to vary smoothly through 2 pi across the spatial extent of the lattice, a baryon number current is induced which in the high density phase remains non-vanishing as |j|->0; we are hence able to extract a quantity characteristic of a superfluid known as the helicity modulus. We also study supercurrent flow at non-zero temperature and estimate the critical temperature at which the normal phase is restored, which is consistent with the conventional picture for thin-film superfluids in which the transition is viewed in terms of vortex -- anti-vortex unbinding.