Superconductor-to-Metal Transitions in Dissipative Chains of Mesoscopic Grains and Nanowires

TL;DR

This paper investigates the quantum phase transitions between superconducting and metallic states in chains of mesoscopic grains and nanowires, highlighting the roles of dissipation and quantum fluctuations.

Contribution

It introduces a detailed analysis of superconductor-to-metal transitions considering dissipation effects, revealing two distinct superconducting phases and complex critical behaviors.

Findings

Existence of two superconducting phases depending on dissipation strength

Identification of super-metallic regimes near phase transitions

Extension of results to nanowires and implications for superconductor-metal transitions

Abstract

The interplay of quantum fluctuations and dissipation in chains of mesoscopic superconducting grains is analyzed, and the results are also applied to nanowires. It is shown that in 1-d arrays of resistively shunted Josephson junctions, the superconducting-normal charge relaxation within the grains plays an important role. At zero temperature, two superconducting phases can exist, depending primarily on the strength of the dissipation. In the fully superconducting phase (FSC), each grain acts superconducting, and the coupling to the dissipative conduction is important. In the SC* phase, the dissipation is irrelevant at long wavelengths. The phase transitions between these two superconducting phases and the normal metallic phase may be either local or global, and possess rich and complex critical properties. These are inferred from both weak and strong coupling renormalization group analyses. At intermediate temperatures, near either superconductor-to-normal phase transition, there are regimes of super-metallic behavior, in which the resistivity first decreases gradually with decreasing temperature before eventually increasing as temperature is lowered further. The results on chains of Josephson junctions are extended to continuous superconducting nanowires and the subtle issue of whether these can exhibit an FSC phase is considered. Potential relevance to superconductor-metal transitions in other systems is also discussed.