Numerical Portrait of a Relativistic Thin Film BCS Superfluid

TL;DR

This paper uses numerical simulations to study a 2+1d relativistic BCS superfluid model, revealing a gapless phase with long-range coherence and no evidence of diquark condensation in high density conditions.

Contribution

It provides the first numerical evidence that the high density phase is a relativistic gapless BCS superfluid without diquark condensation.

Findings

No diquark condensation in high density phase

Presence of long-range phase coherence

Normal Fermi liquid behavior with no energy gap

Abstract

We present results of numerical simulations of the 2+1d Nambu - Jona-Lasinio model with a non-zero baryon chemical potential mu including the effects of a diquark source term. Diquark condensates, susceptibilities and masses are measured as functions of source strength j. The results suggest that diquark condensation does not take place in the high density phase mu>mu_c, but rather that the condensate scales non-analytically with j implying a line of critical points and long range phase coherence. Analogies are drawn with the low temperature phase of the 2d XY model. The spectrum of the spin-1/2 sector is also studied yielding the quasiparticle dispersion relation. There is no evidence for a non-zero gap; rather the results are characteristic of a normal Fermi liquid with Fermi velocity less than that of light. We conclude that the high density phase of the model describes a relativistic gapless thin film BCS superfluid.