Nucleation of superconductivity in a mesoscopic loop of varying width

TL;DR

This paper investigates how the superconducting state evolves in a mesoscopic disk with a varying hole size, revealing a transition from 1D to 2D regimes and effects of asymmetry on critical fields.

Contribution

It provides experimental and theoretical insights into the nucleation of superconductivity in mesoscopic loops with varying geometries and symmetry breaking.

Findings

Transition from 1D to 2D superconducting regimes with increasing magnetic field.

Good agreement between experimental Tc(H) data and Ginzburg-Landau theory.

Enhanced critical field observed in asymmetric structures.

Abstract

We study the evolution of the superconducting state in a perforated disk by varying the size of the hole. The superconducting properties are investigated by means of transport measurements around the superconducting/normal phase boundary Tc(H). A transition from a one-dimensional to a two-dimensional regime is seen when increasing the magnetic field for disks with small holes. A good agreement is found between the measured Tc(H) line and the calculations performed in the framework of the linearized Ginzburg-Landau theory. The effect of breaking the axial symmetry of the structure by moving the hole away from the center of the disk is also studied. An enhanced critical field is found for the asymmetric structures, possibly due to the recovery of the singly connected state.