Volume 79, Number 6, September 2007
Article Number 67003
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 21 August 2007
EPL, 79 (2007) 67003
DOI: 10.1209/0295-5075/79/67003

Topology effects on the heat capacity of mesoscopic superconducting disks

F. R. Ong and O. Bourgeois

Institut Néel, CNRS-UJF - 25 av. des Martyrs, BP 166, 38042 Grenoble Cedex 9, France

received 29 June 2007; accepted in final form 26 July 2007; published September 2007
published online 21 August 2007

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 vs. 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. $C_{{\rm p}}$ vs. H plots exhibit cascades of phase transitions as L increases or decreases by one unit, 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.

74.78.Na - Mesoscopic and nanoscale systems.
74.25.Bt - Thermodynamic properties.
74.25.Dw - Superconductivity phase diagrams.

© Europhysics Letters Association 2007