Multiquantum Vortices in Conventional Superconductors with Columnar Defects Near the Upper Critical Field

TL;DR

This paper theoretically investigates vortex configurations in conventional superconductors with columnar defects near the upper critical field, revealing symmetry-dependent deformations and transitions affecting magnetic properties.

Contribution

It introduces a detailed theoretical analysis of vortex lattice deformations and symmetry transitions caused by columnar defects near the upper critical field in superconductors.

Findings

Defects cause local vortex lattice deformations with $C_3$ or $C_6$ symmetry.

Transitions between vortex configurations lead to jumps in magnetization.

Magnetic susceptibility exhibits discontinuities at transition points.

Abstract

Equilibrium vortex configuration in conventional type II superconductors containing columnar defects is theoretically investigated. Near the upper critical field a single defect causes a strong local deformation of the vortex lattice. This deformation has $C_3$ or $C_6$ point symmetry, whose character strongly depends on the vortex-defect interaction. If the interaction is attractive, the vortices can collapse onto defect, while in the case of repulsion the regions free of vortices appear near a defect. Increasing the applied magnetic field results in an abrupt change of the configuration of vortices giving rise to reentering transitions between configurations with $C_3$ or $C_6$ symmetry. In the case of a small concentration of defects these transitions manifest themselves as jumps of magnetization and discontinuties of the magnetic susceptibility.