INTRINSIC FEATURES OF BI2SR2CACU2O8+DELTA TUNNELING SPECTRA - SCALING AND SYMMETRY OF THE ENERGY-GAP

Tunneling measurements have been made on a series of high-quality Bi2Sr2CaCU2O8+delta (BSCCO) single crystals with transition temperatures (T(c)) ranging from 79 to 92 K. From these systematic studies it has been possible to delineate the intrinsic features of the low-energy electronic spectrum in the BSCCO materials. These results demonstrate that the magnitude of 2DELTA at 4.2 K is nearly constant in the different T(c) samples, and thus, that 2DELTA/kT(c) increases as T(c) decreases. In addition, intrinsic quasiparticle excitations are detected within the gap irrespective of the sample T(c)'s. Analyses of these electronic spectra using a variety of pairing models suggest that gap functions having a large anisotropy can provide a good fit to the experimental data.