Landau quantization and spin polarization of cold magnetized quark matter

TL;DR

This paper studies how strong magnetic fields influence the properties of strange quark matter in compact stars, revealing effects on spin polarization, density thresholds, and oscillations in sound velocity.

Contribution

It introduces a self-consistent quasiparticle model to analyze magnetic and density effects on quark matter, highlighting the magnetic field's role in enhancing spin polarization.

Findings

Magnetic field increases spin polarization in strange quark matter.

Sound velocity oscillates with density, approaching 1/3 at high densities.

Density thresholds for particle alignment depend on individual species.

Abstract

The magnetic field and density behaviors of various thermodynamic quantities of strange quark matter under compact star conditions are investigated in the framework of the thermodynamically self-consistent quasiparticle model. For individual species, a larger number density $n_i$ leads to a larger magnetic field strength threshold that align all particles parallel or antiparallel to the magnetic field. Accordingly, in contrast to the finite baryon density effect which reduces the spin polarization of magnetized strange quark matter, the magnetic field effect leads to an enhancement of it. We also compute the sound velocity as a function of the baryon density and find the sound velocity shows an obvious oscillation with increasing density. Except for the oscillation, similar to the zero-magnetic field case that the sound velocity grows with increasing density and approaches the conformal limit $V_s^2=1/3$ at high densities from below.