Magnetic Field Dependence of the Superconducting Gap and the Pseudogap in Bi2212 andHgBr2-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 ${\mathrm{HgBr}}_2$-Bi2212 high- $T_c$ superconductors. We were able to distinguish with great clarity two coexisting gaps: (i) the superconducting gap, which closes as $H\to H_{c2\mathrm{}}\left(T\right)$, 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.