Crystal structure and superconducting properties in Cu$_{x}$Bi$_{2}$Se$_{3}$

The recent discovery of the anomalous superconductivity in Cu$_{x}$Bi$_{2}$Se$_{3}$ (0.10$<$x$<$0.25) has attracted much attention because of the relation between superconducting state and topological surface state. In order to understand the role of Cu doping in superconducting Bi$_{2}$Se$_{3}$, we study the doping dependence of the magnetic properties and the characteristics of crystal structures. We made high quality of Cu$_{x}$Bi$_{2}$Se$_{3}$ single crystals with several doping level of x by using melt growth technique. We confirmed the superconducting transition from Cu$_{x}$Bi$_{2}$Se$_{3}$ for several doping levels and determined the phase diagram of a function of x. The lattice constant increases with increasing Cu doping level, however it saturated around x=0.25 which corresponds to the saturation of $T_{c}$ as well. We analyzed the crystal structure in detail in explaining the occurrence of superconductivity. Details of the structural and magnetization study will be discussed in the conference.