Spectroscopy study of Hg₁Ba₂Ca₂Cu₃O_8+x by scanning tunneling microscopy

We have measured the tunnel conductance of sintered Hg-1223 superconductor (Tc onset = 133 K) using a low-temperature STM with Au tips. In spite of spatial fluctuations due to sample surface inhomogeneity gap-like structures are found with Δ ≅ 24 ± 2 mV at 4.2 K. These values remain almost constant up to at least 80 K. The usual background conductance is parabolic, and ohmic in fewer cases. Samples melted under high pressure have also been investigated. © 1994.