Evidence for Coexistence of the Superconducting Gap and the Pseudogap in Bi-2212 from Intrinsic Tunneling Spectroscopy

We present intrinsic tunneling spectroscopy measurements on small ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+x}$ mesas. The tunnel conductance curves show both sharp peaks at the superconducting gap voltage and broad humps representing the $c$-axis pseudogap. The superconducting gap vanishes at $T_c$, while the pseudogap exists both above and below $T_c$. Our observation implies that the superconducting and pseudogaps represent different coexisting phenomena.