Strange quark mass turns magnetic domain walls into multi-winding flux tubes

Dense quark matter is expected to behave as a type-II superconductor at strong coupling. It was previously shown that if the strange quark mass m(s) is neglected, magnetic domain walls in the so-called 2SC phase are the energetically preferred magnetic defects in a certain parameter region. Computing the flux tube profiles and associated free energies within a Ginzburg-Landau approach, we find a cascade of multi-winding flux tubes as 'remnants' of the domain wall when m(s) is increased. These flux tubes exhibit an unconventional ring-like structure of the magnetic field. We show that flux tubes with winding numbers larger than one survive for values of m(s) up to about 20% of the quark chemical potential. This makes them unlikely to play a significant role in compact stars, but they may appear in the QCD phase diagram in the presence of an external magnetic field.

Automated summary

Research has shown that when the strange quark mass increases, magnetic domain walls evolve into multi-winding flux tubes with ring-like magnetic field structures. These flux tubes may appear in the QCD phase diagram under certain conditions.