Puzzling evidence for surface superconductivity in the layered dichalcogenide Cu10%TiSe2

Abstract We report on specific heat and magnetotransport measurements performed on superconducting Cu 10 % TiSe 2 single crystals. We show that superconductivity persists in transport measurements up to magnetic fields H R well above the upper critical field H c 2 deduced from the calorimetric measurements. Surprisingly this “surface” superconductivity is present for all magnetic field orientations, either parallel or perpendicular to the layers. For H ‖ ab , the temperature dependence of the H R / H c 2 ratio can be well reproduced by solving the Ginzburg–Landau equations in presence of a surface layer with reduced superconducting properties. Unexpectedly this temperature dependence does not depend on the field orientation.