Hard Superconductivity of a Soft Metal in the Quantum Regime

TL;DR

This paper demonstrates that quantum confinement in a soft metal enables the stabilization of superconductivity in ultra-thin, nanoscale geometries, showing robust supercurrents and vortex trapping, with potential for nanoscale superconducting applications.

Contribution

It introduces a method to achieve stable superconductivity in ultra-thin, quantum-confined soft metal structures, revealing their robustness and vortex trapping capabilities.

Findings

Superconductivity persists in millimeter-wide, atomic-layer-thick soft metal structures.

Supercurrents reach up to 10% of the depairing current density.

Quantum trapping of vortices contributes to the extreme hardness of the critical state.

Abstract

Superconductivity is inevitably suppressed in reduced dimensionality. Questions of how thin superconducting wires or films can be before they lose their superconducting properties have important technological ramifications and go to the heart of understanding coherence and robustness of the superconducting state in quantum-confined geometries. Here, we exploit quantum confinement of itinerant electrons in a soft metal to stabilize superconductors with lateral dimensions of the order of a few millimeters and vertical dimensions of only a few atomic layers. These extremely thin superconductors show no indication of defect- or fluctuation-driven suppression of superconductivity and sustain supercurrents of up to 10% of the depairing current density. The extreme hardness of the critical state is attributed to quantum trapping of vortices. This study paints a conceptually appealing, elegant picture of a model nanoscale superconductor with calculable critical state properties. It indicates the intriguing possibility of exploiting robust superconductivity at the nanoscale.