Quantum Phase Transitions and Particle-Hole Pair Transport in Capacitively Coupled Josephson-Junction Chains

TL;DR

This paper studies quantum phase transitions and particle-hole pair transport in capacitively coupled Josephson-junction chains, revealing how pair condensation induces superconductivity and supercurrent drag at zero temperature.

Contribution

It introduces a detailed analysis of particle-hole pair dynamics and their role in quantum phase transitions in coupled Josephson-junction chains.

Findings

Particle-hole pairs dominate transport phenomena.

Condensation of pairs leads to superconducting state.

Supercurrents are perfectly dragged between chains.

Abstract

We consider two chains of ultrasmall Josephson junctions, coupled capacitively with each other, and investigate the transport of particle-hole pairs and the quantum phase transitions at zero temperature. For appropriate parameter ranges, the particle-hole pairs are found to play major roles in transport phenomena; condensation of such pairs leads to the superconducting state, displaying perfect drag of supercurrents along the two chains.