Phase and Vortex Correlations in Superconducting Josephson-Junction Arrays at Irrational Magnetic Frustration

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. (AU)