Magnetic Field Driven Quantum Phase Transitions in Josephson Arrays

TL;DR

This study investigates magnetic-field-induced quantum phase transitions in Josephson junction arrays, revealing duality in energies and an intermediate 'bad metal' regime influenced by vortex pinning and disorder.

Contribution

It provides new insights into the energy characteristics and phase behavior of Josephson arrays under magnetic fields, highlighting the role of coupling strength and disorder.

Findings

Duality between superconducting and insulating energies in strongly coupled arrays

Observation of a 'bad metal' regime in weakly coupled arrays under magnetic fields

Vortex pinning and disorder influence phase transitions and inhomogeneity

Abstract

We have studied the magnetic-field-driven quantum phase transitions in Josephson junction arrays with a large coordination number. The characteristic energies were extracted in both the superconducting and insulating phases by integrating the current-voltage characteristics over a voltage range 2eV\leqk_B T. For the arrays with a relatively strong Josephson coupling, we observed duality between the energies in the superconducting and insulating phases. The arrays with a weaker Josephson coupling demonstrate an intermediate, "bad metal" regime in weak magnetic fields; this observation underlines the importance of vortex pinning at large scales and, presumably, emergent inhomogeneity in the presence of strong offset charge disorder.