Pairing Symmetry and Magnetic Relaxation in Topological Superconductor CuxBi2Se3

Topological insulators are materials with a bulk-insulating gap, exhibiting a quantum-Hall-effect-like behavior in the absence of a magnetic field. The experimental as well as theoretical study show Bi2Se3 has a single surface Dirac cone associated with the topologically protected surface state against time reversal symmetry. CuxBi2Se3 is of particular interest because of the signature of superconductivity found at low temperatures. Here we report the growth and the observation of bulk superconductivity from dc magnetization measurements in a cylindrical single crystal of CuxBi2Se3. The magnitude of the magnetization in the Meissner state is very small and the magnetic field dependence of the magnetization just above the lower critical field Hc1 is very different from those of usual type II superconductors. We believe that superconductivity observed in CuxBi2Se3 is consistent with the spin-triplet pairing superconductivity with odd parity. We also observed a rapid relaxation phenomenon of the diamagnetic magnetization, indicating the flexible motion of the vortices in that temperature and field regime.