Pion superfluid phase transition under external magnetic field including inverse magnetic catalysis effect

TL;DR

This paper investigates how external magnetic fields and the inverse magnetic catalysis effect influence the pion superfluid phase transition using a regularized NJL model, revealing that magnetic fields generally disfavor pion superfluidity.

Contribution

It introduces the inverse magnetic catalysis effect via a magnetic field dependent coupling in the NJL model to study pion superfluidity under magnetic fields.

Findings

Critical isospin chemical potential increases with magnetic field.

Magnetic field disfavors pion superfluid phase.

Inverse magnetic catalysis shifts critical values higher.

Abstract

Pion superfluid phase transition under external magnetic field including the inverse magnetic catalysis (IMC) effect is investigated by the Pauli-Villars regularized NJL model. Based on the Goldstone's theorem, we apply the massless Goldstone boson ($\pi^+$ meson) to determine the onset of pion superfluid phase. The inverse magnetic catalysis effect is introduced by the magnetic field dependent coupling $G(eB)$, which is a decreasing function of magnetic field. At fixed temperature and baryon chemical potential, the critical isospin chemical potential for pion superfluid phase transition including IMC effect increases as the magnetic field grows, which is similar as the case without IMC effect. This demonstrates that magnetic field disfavors the pion superfluid phase when considering or ignoring IMC effect. The critical isospin chemical potential at fixed magnetic field, temperature and baryon chemical potential is shifted to higher value by the IMC effect. Since it is more difficult to form pion superfluid with weaker coupling.