Type-I/type-II transition in proton superconductivity

Determine the density at which proton superconductivity transitions from type II to type I and establish whether such a transition occurs in neutron-star matter.

Background

The type-I/type-II classification can be modified by entrainment, density couplings, gradient couplings, medium polarization, and the nuclear interaction model. The occurrence and location of the transition are therefore unresolved.

References

The density at which the proton superconductor crosses from type-II to type-I behavior --- and whether such a transition occurs at all --- remains uncertain.

— Superfluidity and Vortex Dynamics in Neutron Stars  (2609.01022 - Link et al., 1 Sep 2026) in Section “Open questions and perspectives” under “Type-I superconductivity”