C. Marcenat

Evidence for Two Superconducting Energy Gaps in MgB2 by Point-Contact Spectroscopy

Experimental support is found for the multiband model of the superconductivity in the recently discovered system MgB(2) with the transition temperature T(c) = 39 K. By means of Andreev reflection, evidence is obtained for two distinct superconducting energy gaps. The sizes of the two gaps ( Delta(S) = 2.8 meV and Delta(L) = 7 meV) are, respectively, smaller and larger than the expected weak coupling value. Because of the temperature smearing of the spectra the two gaps are hardly distinguishable at elevated temperatures, but when a magnetic field is applied the presence of two gaps can be demonstrated close to the bulk T(c) in the raw data.

Dependence of the superconducting transition temperature on the doping level in single crystalline diamond films.

Homoepitaxial diamond layers doped with boron in the 10(20)-10(21) cm(-3) range are shown to be type II superconductors with sharp transitions (approximately 0.2 K) at temperatures increasing from 0 to 2.1 K with boron contents. The critical concentration for the onset of superconductivity in those 001-oriented single-crystalline films is about 5-7 10(20) cm(-3). The H-T phase diagram has been obtained from transport and ac-susceptibility measurements down to 300 mK.

Anisotropy of the upper critical field and critical current in single crystal MgB2

We report on specific-heat, high-magnetic-field transport, and ac-susceptibility measurements on

Anisotropies of the lower and upper critical fields in MgB2 single crystals

{\mathrm{MgB}}_{2}

Tunneling spectroscopy and vortex imaging in boron-doped diamond.

single crystals. The upper critical field for magnetic fields perpendicular and parallel to the basal planes is presented in the entire temperature range. A very different temperature dependence has been observed in the two directions, which yields a temperature-dependent anisotropy with

Metal-to-insulator transition and superconductivity in boron-doped diamond

\ensuremath{\Gamma}\ensuremath{\sim}5

Thermodynamic phase diagram of Fe(Se0.5Te0.5) single crystals in fields up to 28 tesla

at low temperatures and

Low-temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers

\ensuremath{\sim}2

Doping-induced metal-insulator transition in aluminum-doped 4H silicon carbide

near

Two-band effects in the angular dependence of H{sub c2} of MgB{sub 2} single crystals.

{T}_{c}.