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.
@article{arxiv.cond-mat/9802199,
title = {Quantum Phase Transitions and Particle-Hole Pair Transport in Capacitively Coupled Josephson-Junction Chains},
author = {Mahn-Soo Choi and M. Y. Choi and Sung-Ik Lee},
journal= {arXiv preprint arXiv:cond-mat/9802199},
year = {2007}
}