Tunneling spectroscopy of Bi2Sr2CaCu2O8+δ/Zn junctions

We present tunneling spectroscopy on as-grown Bi2Sr2CaCu2O8+delta (Bi2212) single crystals taken with Bi2212/Zn tunnel junctions. The measured temperature-dependent tunneling conductance show a sharp quasiparticle peak at the gap voltage at low temperature, and the suppression of conductance in gap region at T above T-c, revealing the opening of a pseudogap. The observed opening temperature of the pseudogap, T*, is above 270K for the investigated as-grown Bi12212. The plots of normalized zero bias conductance versus T, G(0,T), provide T, of the region investigated in the crystals, and the G(0,T) can be fitted well to a T-2 law for T below T-c, which provides a new evidence of d-wave symmetry pairing in Bi2212.