Phase and vortex correlations in Josephson-junction arrays at irrational frustration

TL;DR

This study uses Monte Carlo simulations to analyze phase coherence and vortex order in Josephson-junction arrays at irrational frustration, revealing a zero-temperature phase transition with distinct correlation lengths for phase and vortex variables.

Contribution

It provides the first detailed scaling analysis showing decoupled phase and vortex transitions with different critical exponents in such arrays.

Findings

Critical temperature vanishes with a power-law divergence of correlation length.

Different critical exponents for phase and vortex variables.

Evidence for a decoupled zero-temperature phase transition.

Abstract

Phase coherence and vortex order in a Josephson-junction array at irrational frustration are studied by extensive Monte Carlo simulations using the parallel tempering method. A scaling analysis of the correlation length of phase variables in the full equilibrated system shows that the critical temperature vanishes with a power-law divergent correlation length and critical exponent $\nu_{ph}$, in agreement with recent results from resistivity scaling analysis. A similar scaling analysis for vortex variables reveals a different critical exponent $\nu_{v}$, suggesting that there are two distinct correlation lengths associated with a decoupled zero-temperature phase transition.