Chiral crystals in strong-coupling lattice QCD at nonzero chemical potential

TL;DR

This paper investigates the phase structure of strong-coupling lattice QCD at nonzero chemical potential, proposing the existence of a chiral density wave phase that breaks symmetries, but finds it unstable in mean-field theory due to lattice artifacts.

Contribution

It introduces the possibility of a crystalline chiral density wave phase in lattice QCD at high chemical potential and analyzes its stability and lattice artifact effects.

Findings

Chiral density wave phase may exist at high chemical potential.

Lattice artifacts influence the stability of this phase.

Fine lattices are needed to observe this phase in simulations.

Abstract

We study the effective action for strong-coupling lattice QCD with one-component staggered fermions in the case of nonzero chemical potential and zero temperature. The structure of this action suggests that at large chemical potentials its ground state is a crystalline `chiral density wave' that spontaneously breaks chiral symmetry and translation invariance. In mean-field theory, on the other hand, we find that this state is unstable. We show that lattice artifacts are partly responsible for this, and suggest that if this phase exists in QCD, then finding it in Monte-Carlo simulations would require simulating on relatively fine lattices. In particular, the baryon mass in lattice units, m_B, should be considerably smaller than its strong-coupling limit of m_B~3.