Superconducting nanoribbon with a constriction: A quantum-confined Josephson junction

TL;DR

This paper investigates how a constriction in superconducting nanoribbons creates a quantum-confined Josephson junction with tunable properties, offering new ways to engineer superconducting quantum devices.

Contribution

It demonstrates that a constriction in superconducting nanoribbons forms a quantum-confined Josephson junction with tunable characteristics based on geometry and gating.

Findings

Constricted nanoribbons exhibit quantum-resonant superconducting gaps.

The constriction acts as a tunable Josephson junction.

Performance depends on constriction length, width, and gating.

Abstract

Extended defects are known to strongly affect nanoscale superconductors. Here we report the properties of superconducting nanoribbons with a constriction formed between two adjacent step-edges, by solving the Bogoliubov-de Gennes equations self-consistently in the regime where quantum confinement is important. Since the quantum resonances of the superconducting gap in the constricted area are different from the rest of the nanoribbon, such constriction forms a quantum-confined S-S'-S Josephson junction, with a broadly tunable performance depending on the length and width of the constriction with respect to the nanoribbon, and possible gating. These findings provide an intriguing approach to further tailor superconducting quantum devices where Josephson effect is of use.