Chiral spiral induced by a strong magnetic field

TL;DR

This paper investigates how strong magnetic fields drastically alter the chiral phase structure of QCD, eliminating the tricritical point and inducing a chiral spiral phase, with effects depending on quark mass and magnetic field strength.

Contribution

It introduces a systematic way to incorporate magnetic field effects into a Ginzburg-Landau framework and analyzes the resulting phase diagram modifications near the chiral critical point.

Findings

Magnetic field removes the tricritical point in the chiral limit.

Chiral spiral phase emerges under strong magnetic fields.

Current quark mass delays the formation of the chiral spiral phase.

Abstract

We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it totally washes the tricritical point out of the phase diagram, bringing the continent for the chiral spiral. This is the case no matter how small is the intensity of the magnetic field. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.