Deconfinement of vortices with continuously variable fractions of the unit flux quanta in two-gap superconductors

摘要

We propose a new stage of confinement-deconfinement transition, which can be observed in laboratory. In two-gap superconductors (SCs), two kinds of vortex exist and each of them carries a continuously variable fraction of the unit flux quanta Φ0 = hc/2e. The confined state of these two is a usual vortex and stable in the low-temperature region of the system under a certain magnetic field above Hc1. We see an analogy to quarks in a charged pion. An entropy gain causes two fractional vortices to be deconfined above a certain temperature.