Chiral and Diquark condensates at large magnetic field in two-flavor superconducting quark matter

TL;DR

This paper investigates how strong magnetic fields influence chiral and diquark condensates in dense two-flavor quark matter using a NJL model, revealing phase transition behaviors relevant to neutron star interiors.

Contribution

It provides a detailed analysis of the magnetic field effects on condensate interdependence and phase transitions in dense quark matter, highlighting the disruption of mixed phases at high magnetic fields.

Findings

Qualitative agreement with zero-field results for B < 10^{18} G.

Weakened phase transitions at moderate magnetic fields.

Transition from crossover to first-order at high magnetic fields for large G_D/G_S.

Abstract

We study the effect of a large magnetic field on the chiral and diquark condensates in a regime of moderately dense quark matter. Our focus is on the inter-dependence of the two condensates through non-perturbative quark mass and strong coupling effects, which we address in a 2-flavor Nambu-Jona-Lasinio (NJL) model. For magnetic fields $eB\lesssim 0.01$ GeV$^2$ (corresponding to $B\lesssim 10^{18}$G), our results agree qualitatively with the zero-field study of Huang et al., who found a mixed broken phase region where the chiral and superconducting gap are both non-zero. For $eB\gtrsim 0.01$ GeV$^2$ and moderate diquark-to-scalar coupling ratio $G_D/G_S$, we find that the chiral and superconducting transitions become weaker but with little change in either transition density. For large $G_D/G_S$ however, such a large magnetic field disrupts the mixed broken phase region and changes a smooth crossover found in the zero-field case to a first-order transition at neutron star interior densities.