Power Law Behavior of the Zero Bias Tunneling Conductance: the New Evidence for d-Wave Symmetry

We report temperature-dependent behavior of the zero bias tunneling conductance (ZBTC), derived from tunneling spectroscopies on as-grown Bi₂Sr₂CaCu₂O_8+δ (Bi2212) single crystals taken with evaporated Zn and Pb planar junctions. At T_c the measured ZBTC shows a kink which gives an in situ measure of the superconducting transition temperature (T_c). Below T_c, the T² dependence of the ZBTC has been observed repeatedly as a new evidence of the d-wave symmetry in Bi2212.