Interlayer tunneling spectroscopy for slightly overdoped Bi2Sr2CaCu2O8+δ

We have measured the interlayer tunneling characteristics of slightly overdoped Bi2Si2CaCu2O8+delta in the c-axis direction from 10 to 220 K by using very thin mesas containing approximately ten CuO2 double layers, The superconducting gap 2 Delta is 50 meV at 10 K and shows a temperature (T) dependence similar to that of the BCS theory. A pseudogap evolves below 150 K, where the c-axis resistivity rho(c) is semiconducting. The normal-state tunneling resistance R-N shows a linear T dependence down to T-c exhibits an abrupt decrease at T-c, and saturates at low T. This reflects scattering arising from an electronic interaction that is relevant to the high-T-c superconductivity.