Interlayer tunneling spectroscopy and doping-dependent energy-gap structure of the trilayer superconductor Bi2Sr2Ca2Cu3O10+δ -: art. no. 054533

The superconducting gap, the pseudogap, and their doping and temperature dependences have been measured by the short-pulse interlayer tunneling spectroscopy for the CuO2 triple-layer high-T-c superconducting Bi2Sr2Ca2Cu3O10+delta system. It is found for a nearly optimally doped sample that the superconducting gap magnitude is approximate to80 meV and the pseudogap is approximate to120 meV, the values of which are slightly larger than those for CuO2 double-layer system. Both gap magnitudes show a clear tendency to decrease with increasing doping. In an underdoped sample, a clear dip-and-hump structure is observed, which declines with increasing doping and tends to diminish in overdoped samples. The relationship between unchanged T-c and decreasing superconducting gap in the overdoped region is discussed in terms of the proximity effect applied to the inequivalent doping model. We also discuss the dip-and-hump structure in comparison with other spectroscopic results. Finally, we argue an important implication of the increasing maximum Josephson current and the decreasing superconducting gap magnitude, both with increasing doping.