QUANTUM VORTICES NEAR THE SUPERCONDUCTOR-INSULATOR TRANSITION IN JOSEPHSON-JUNCTION ARRAYS

We investigate the properties of vortices in Josephson junction arrays in the regime close to the superconductor-insulator transition. We de rive general expressions for the vortex mass and the vortex-spinwave c oupling in terms of the charge-charge correlation function, which we e valuate in a self consistent harmonic approximation, as well as by mea ns of Monte Carlo simulations. Our main conclusions are that close to the transition to the insulating phase the vortex mass vanishes and th e treshhold velocity above which vortices couple to spinwaves diverges . Thus, in the quantum regime close to the phase transition there is a velocity window in which vortices may move ballistically without damp ing, this in contrast to the flux flow behaviour in classical arrays.