Superconducting nanobridges under magnetic fields

TL;DR

This paper investigates the behavior of superconducting lead nanobridges and nanotips under high magnetic fields, combining experimental measurements with theoretical modeling to understand their superconducting properties and fluctuations.

Contribution

It provides new experimental data and theoretical insights into the effects of magnetic fields on superconducting nanostructures, including modeling of the order parameter and fluctuation effects.

Findings

Superconducting nanotips remain stable under 2 T magnetic field.

Asymmetric nanobridges exhibit two-step loss of Andreev current.

Thermal fluctuations influence Josephson coupling in nanobridges.

Abstract

We report on the study of superconducting nanotips and nanobridges of lead with a Scanning Tunnelling Microscope in tunnel and point contact regimes. We deal with three different structures. A nanotip that remains superconducting under a field of 2 T. For this case we present model calculations of the order parameter, which are in good agreement with the experiments. An asymmetric nanobridge of lead showing a two steps loss of the Andreev excess current due to different heating and dissipation phenomena in each side of the structure. A study of the effect of the thermal fluctuations on the Josephson coupling between the two sides of a superconducting nanobridge submitted to magnetic fields. The different experiments were made under magnetic fields up to twenty five times the volume critical field of lead, and in a temperature range between 0.6 K and 7.2 K.