MODELING OF TUNNELING SPECTROSCOPY IN HIGH-T-C SUPERCONDUCTORS INCORPORATING BAND-STRUCTURE, GAP SYMMETRY, GROUP-VELOCITY, AND TUNNELING DIRECTIONALITY

A theoretical model for tunneling spectroscopy employing tight-binding band structure, d(x2-y2) gap symmetry, group velocity, and tunneling directionality is studied. This is done to investigate if the model ca n exhibit the same wide range of characteristics observed in tunneling experiments on high-T-c superconductors. A band structure specific to optimally-doped Bi2Sr2CaCu2O8 (Bi-2212) is used to calculate the tunn eling density of states for a direct comparison to experimental tunnel ing conductance. A robust feature of the model is an asymmetric, decre asing conductance background, which is in agreement with experiment fo r Bi-2212. The model also produces generally good agreement with the t unneling data, especially in the gap region. In particular, the experi mentally observed asymmetric conductance peaks can be understood with this model as a direct consequence of the d(x2-y2) gap symmetry. Dip f eatures observed at \eV\similar to 2 Delta in the experimental data me not found for any range of parameters in this model. indicating that these features are caused by other physical mechanisms such as strong- coupling effects. [S0163-1829(98)00525-6].