Electronic Structure, Irreversibility Line and Magnetoresistance of Cu0.3Bi2Se3 Superconductor**Supported by the National Natural Science Foundation of China under Grant Nos 11190022, 91021006 and 11374338, the National Basic Research Program of China under Grant Nos 2011CB921703, 2011CBA00110 and 2013CB921700, and the Strategic Priority Research Program(B) of the Chinese Academy of Sciences under Grant No XDB07020300.

Abstract

CuxBi2Se3 is a superconductor that is a potential candidate for topological superconductors. We report our laser-based angle-resolved photoemission measurement on the electronic structure of the CuxBi2Se3 superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi2Se3 topological insulator remains robust after the Cu-intercalation, while the Dirac cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper critical field at zero temperature of ∼4000 Oe for the Cu0.3Bi2Se3 superconductor with a middle point Tc of 1.9K. The relation between the upper critical field Hc2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cu0.3Bi2Se3 superconductors up to room temperature. These observations provide useful information for further study of this possible candidate for topological superconductors.