Discrimination between the superconducting gap and the pseudo-gap in Bi2212 from intrinsic tunneling spectroscopy in magnetic field

Intrinsic tunneling spectroscopy in high magnetic field is used for a direct test of superconducting features in a quasiparticle density of states (DOS) of high-$T_c$ superconductors. We were able to distinguish with a great clarity two co-existing gaps in the tunneling DOS with strikingly different magnetic field ($H$) and temperature ($T$) dependencies: (i) the superconducting gap, which closes both as $H \to H_{c2}(T)$ and $T\to T_c(H)$ and (ii) non-superconducting $c$-axis pseudo-gap, which does not change neither with $H$, nor $T$. This speaks against the precursor superconductivity origin of the $c$-axis pseudo-gap.