Spontaneous spin polarization due to tensor self-energies in quark matter

Abstract

We study the magnetic properties of quark matter in the Nambu--Jona-Lasinio model with the tensor interaction. The spin-polarized phase given by the tensor interaction survives even when the quark mass is zero, while that given by the axial-vector interaction disappears. There are two kinds of spin-polarized phases: one appears in the chiral-broken phase, and the other in the chiral-restored phase where the quark mass is zero. The latter phase can appear independently of the strength of the tensor interaction.