Second-order multiple-quanta flux entry into a perforated spherical mesoscopic superconductor

Ben Xu; M. V. Milošević; F. M. Peeters

doi:10.1103/PhysRevB.82.214501

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Second-order multiple-quanta flux entry into a perforated spherical mesoscopic superconductor

Ben Xu, M. V. Milošević, F. M. Peeters

DOI 10.1103/PhysRevB.82.214501 · Physical Review B

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Abstract

Flux entry in type-II superconductors without prominent symmetry is a first-order phase transition, where flux enters conventionally gradual in units of a flux quantum. Here we show that neither is necessarily the case in a mesoscopic superconducting sphere with a perforation. In axially applied magnetic field, vortices initially occupy the hole, and can oppose further flux entry in the sample. As a result, multiple-quanta flux entry is found at significantly higher field, and it can manifest as a second-order transition due to suppressed geometric barrier at the equatorial belt of the sample. At high fields a new state is found, with gradually destroyed condensate from the equator inwards, the exact opposite of surface superconductivity.