STRONG DEPENDENCE OF THE SUPERCONDUCTING GAP ON OXYGEN DOPING FROM TUNNELING MEASUREMENTS ON BI2SR2CACU2O8-DELTA

Tunneling measurements are reported for break junctions on Bi2Sr2CaCu2 O8-delta Single crystals with various oxygen concentrations. Supercond ucting energy gaps a are observed in the underdoped samples which are considerably larger (similar to 30%) than found in optimal doped cryst als. The trend of decreasing Delta and 2 Delta/kT(c), with increasing hole doping is continued into the overdoped region. Thus the supercond ucting gap and strong-coupling ratio change monotonically and dramatic ally over a narrow doping region where T-c, exhibits a maximum.