Localized High-Tc Superconductivity on the Surface of Na-Doped WO3

摘要: WO3 crystals were doped with Na on the surface to ∼7% nominal atomic concentration. Scanning tunneling microscopy and spectroscopy employed, together magnetization measurements, in study of these crystals. Tunneling experiments reveal superconducting islands, 20–150 nm size, covering about 10% surface, rest which is insulating. Magnetization measurements show that phase formed at has a critical temperature 91 K, while yields gaps having values up 2Δ/kT c ∼ 4. Presumably most sodium concentrated islands therefore they are metallic nature, above 30% This material noncuprate superconductor high temperature.