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 c2 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 c2 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.

Magnetic and thermodynamic properties of CuxTiSe2 single crystals

“…For all samples ∆T c /T c is smaller than 0.08, ∆T c being the transition width calculated between 10% and 90% of the specific heat anomaly. For the best sample, sample G, it is as small as 0.025.The specific-heat properties of samples A, B, C, and D were previously investigated into detail in [8] (same sample labeling); specific heat of the sample G was presented in [16]. the inset of Fig.4b].…”