Thermal signatures of Little-Parks effect in the heat capacity of mesoscopic superconducting rings

TL;DR

This study measures the thermal signatures of the Little-Parks effect in mesoscopic superconducting rings using a highly sensitive nanocalorimeter, revealing flux-dependent heat capacity oscillations consistent with Ginzburg-Landau theory.

Contribution

First experimental observation of thermal signatures of the Little-Parks effect in nanoscale superconducting rings via attojoule calorimetry.

Findings

Heat capacity $C_p$ oscillates with magnetic flux $\Phi$ near $T_c$

$C_p$ jump at transition is flux-dependent and oscillates with period $\Phi_0$

Results agree with Ginzburg-Landau theory

Abstract

We present the first measurements of thermal signatures of the Little-Parks effect using a highly sensitive nanocalorimeter. Small variations of the heat capacity $C\_p$ of 2.5 millions of non interacting micrometer-sized superconducting rings threaded by a magnetic flux $\Phi$ have been measured by attojoule calorimetry. This non-invasive method allows the measurement of thermodynamic properties -- and hence the probing of the energy levels -- of nanosystems without perturbing them electrically. It is observed that $C\_p$ is strongly influenced by the fluxoid quantization (Little-Parks effect) near the critical temperature $T\_c$. The jump of $C\_p$ at the superconducting phase transition is an oscillating function of $\Phi$ with a period $\Phi\_0=h/2e$, the magnetic flux quantum, which is in agreement with the Ginzburg-Landau theory of superconductivity.