Pseudogap behavior revealed in interlayer tunneling in overdoped Bi2Sr2CaCu2O8+x

We report on heating-compensated interlayer tunneling spectroscopy (ITS) performed on stacks of overdoped Bi2Sr2CaCu2O8+x intrinsic junctions, where most of the bias-induced heating in the ITS was eliminated. The onset temperature of a pseudogap (PG), which was revealed in the hump structure of the electronic excitation spectra, nearly reached room temperature for our overdoped intrinsic junctions, which represented the genuine PG onset. At a temperature below but close to T-c, both the superconducting coherence peak and the pseudogap hump coexisted, implying that the two gaps are of separate origins. The hump voltage increased below T-c, following the superconducting gap voltage, which led to the conclusion that the hump structure below T-c in our ITS arose from the combined contributions of the quasiparticle spectral weights of two different characters: one of the superconducting state and another of the PG state near the antinodal region.