Effect of charging energy on transition temperature of granular superconductors

The effect of the zero-point fluctuations of the phase on the transition temperature Tsub(c) of a granular superconductor is calculated using a model which takes into account the short-range part of the charging energy. A self-consistent mean field theory predicts a critical value of the ratio of the Josephson coupling constant to the charging energy and the existence of two values of Tsub(c), indicating the possibility of re-entrance into normal state at the lower one. (author)