Specific heat measurement of mesoscopic loops

TL;DR

This study presents highly sensitive specific heat measurements of mesoscopic superconducting loops, revealing unique thermal behaviors, phase transitions, and metastable states that differ from bulk materials, and are well explained by Ginzburg-Landau theory.

Contribution

The paper introduces a novel measurement technique for mesoscopic loops and demonstrates detailed thermal properties and phase transition behaviors in these systems.

Findings

Observation of discrete jumps in specific heat indicating phase transitions.

Variation of transition periodicity with temperature.

Agreement of experimental results with Ginzburg-Landau theory.

Abstract

We report highly sensitive specific heat measurement on mesoscopic superconducting loops at low temperature. These mesoscopic systems exhibit thermal properties significantly different from that of the bulk materials. The measurement is performed on a silicon membrane sensor where 450 000 superconducting aluminium loops are deposited through electron beam lithography under an applied magnetic field. Each entry of a vortex is associated to a jump in the specific heat of few thousands of Boltzmann constant kB indicating the existence of phase transitions. The periodicity of this sequential phase transitions is a nontrivial behaviour and varies strongly as the temperature is decreased. The successive phase transitions are well described by the Ginzburg-Landau theory of superconductivity. The presence of metastable states is responsible for the n-0 (n=1, 2, 3...) periodicity of the discontinuities of the measured specific heat.