Quantum vortex dynamics in a Josephson junction array frustrated by external charges

Abstract

We study the effect of a uniform background of external charges on the superconductor - insulator phase transition and on single-vortex properties, such as mass and damping, in a quantum (zero-temperature) Josephson junction array, in the case of long-range Coulomb interaction between Cooper pairs. We find, by an analytical method based on a small- expansion, that the phase transition moves quickly to higher with increasing offset charge, indicating that external charges significantly stabilize the superconducting phase. At the transition the vortex mass vanishes and the spin-wave damping decreases, as a consequence of the suppression of charge fluctuations, while upon decreasing , we confirm the `classical' result for the mass and the damping, independently of the external charges.