QUANTUM CHARGE FLUCTUATIONS AND GLOBAL SUPERCONDUCTIVITY OF JOSEPHSONMEDIA - PATH-INTEGRAL MONTE-CARLO SIMULATIONS

The effect of quantum charge fluctuations on the global superconductin g state of Josephson media (arrays of microscopic Josephson junctions, films consisting of tiny granules, etc.) is considered. Path integral Monte Carlo simulations are used. The system is described by the 2 1 XY-model. The dependences of potential, kinetic and total energy, an d mean square fluctuations of phases versus the temperature rand the q uantum parameter q = ($) over bar h/root JC are studied (J is the Jose phson constant and C is the granule electrical capacity). The phase tr ansition line T-c=T-c(q) was determined by using the dependences of th e helicity modulus versus the temperature and the quantum parameter q. The helicity modulus drops to zero at the phase transition line T=T-c (q). The quasi-3D behaviour in the quantum region of the phase diagram T-q is discussed.