Non-mean-field behavior and Tcenhancement in granular microbridges

New measurements of critical current Icin granular Al microbridges are presented. They show, near the critical temperature Tc, a departure from the mean-field behavior (linear dependence of Ic^2/3on T). Enhancement of Icby microwaves is simultaneously observed, up to Tc. The results point out to a Tcenhancement (by ∼ 10 mK). A numerical model, which depicts the shape of the Ic^2/3(T) curve, is presented. The model also explains the co-existence of microwave enhancement, and can account for non-linear Ic^2/3(T) curves measured by others.