"Superconductor-Insulator transition" in a single Josephson junction

TL;DR

This paper investigates the superconductor-insulator transition in a single Josephson junction by analyzing VI-curves, revealing a crossover linked to a dissipative phase transition and comparing experimental results with theoretical predictions.

Contribution

It provides experimental evidence of the superconductor-insulator transition in Josephson junctions and compares observed phase diagrams with theoretical models considering measurement accuracy and thermal effects.

Findings

Crossover in VI-curves indicates superconductor-insulator transition.

Measured phase diagram aligns with a theory including measurement and thermal fluctuations.

Resistance bump at zero-bias signifies the transition point.

Abstract

VI-curves of resistively shunted single Josephson junctions with different capacitances and tunneling resistances are found to display a crossover between two types of VI-curves: one without and another with a resistance bump (negative second derivative) at zero-bias. The crossover corresponds to the dissipative phase transition (superconductor-insulator transition) at which macroscopic quantum tunneling delocalizes the Josephson phase and destroys superconductivity. Our measured phase diagram does not agree with the diagram predicted by the original theory, but does coincide with a theory that takes into account the accuracy of voltage measurements and thermal fluctuations.