Reentrant behavior of the phase stiffness in Josephson junction arrays

TL;DR

This paper investigates the phase diagram of a 2D Josephson junction array with high substrate resistance, revealing a reentrant phase stiffness behavior near a quantum critical point due to quantum fluctuations.

Contribution

It provides the first detailed Monte Carlo analysis showing reentrant phase stiffness in a quantum XY model of Josephson arrays near a quantum critical threshold.

Findings

Reentrant phase stiffness observed near the quantum critical point.

Superconducting phase disappears at low temperatures due to quantum fluctuations.

A threshold quantum coupling g* marks the boundary of phase coherence.

Abstract

The phase diagram of a 2D Josephson junction array with large substrate resistance, described by a quantum XY model, is studied by means of Fourier path-integral Monte Carlo. A genuine Berezinskii-Kosterlitz-Thouless transition is found up to a threshold value g* of the quantum coupling, beyond which no phase coherence is established. Slightly below g* the phase stiffness shows a reentrant behavior with temperature, in connection with a low-temperature disappearance of the superconducting phase, driven by strong nonlinear quantum fluctuations.