Magnetic field dependence of the superconducting gap and the pseudogap in Bi2212 and HgBr2-Bi2212, studied by intrinsic tunneling spectroscopy

Intrinsic tunneling spectroscopy in high magnetic field (H) is used for a direct test of superconducting features in the quasiparticle density of states of pure Bi2212 and intercalated HgBr2-Bi2212 high-T-c, superconductors. We were able to distinguish with great clarity two coexisting gaps: (i) the superconducting gap, which closes as H -> H-c2(T), and (ii) the c-axis pseudogap, which does not change either with H or with T. Strikingly different H dependencies, together with previously observed different temperature dependencies of the two gaps, speak against a superconducting origin of the pseudogap.