Topology effects on the heat capacity of mesoscopic superconducting disks

TL;DR

This study investigates how topology influences heat capacity in mesoscopic superconducting disks, revealing non-periodic modulations, vortex state cascades, and phase transition behaviors through heat capacity measurements.

Contribution

It demonstrates the impact of topology on vortex states and phase transitions in mesoscopic superconductors, including the first experimental evidence of temperature-driven vortex state transitions.

Findings

Non-periodic modulations of heat capacity with magnetic field.

Cascades of phase transitions linked to vortex number changes.

Phase diagrams of vortex states in superconducting disks.

Abstract

Phase transitions in superconducting mesoscopic disks have been studied over the H-T phase diagram through heat capacity measurement of an array of independent aluminium disks. These disks exhibit non periodic modulations versus H of the height of the heat capacity jump at the superconducting to normal transition. This behaviour is attributed to giant vortex states characterized by their vorticity L. A crossover from a bulk-like to a mesoscopic behaviour is demonstrated. $C_{\rm p}$ versus H plots exhibit cascades of phase transitions as L increases or decreases by one unity, with a strong hysteresis. Phase diagrams of giant vortex states inside the superconducting region are drawn in the vortex penetration and expulsion regimes and phase transitions driven by temperature between vortex states are thus predicted in the zero field cooled regime before being experimentally evidenced.