The Fermi Surface of Highly Doped Bi$_{2}$Se$_{3}$ and the Implications for Superconductivity in CuBi$_{2}$Se$_{3}$

The 3D Fermi-surface (FS) mapping of Bi$_{2}$Se$_{3}$ for different samples with carrier-density ranging from $10^{17}$ to $10^{20}$ cm$^{-3}$ was made using Angle Resolved Photoemission Spectroscopy. While in the low carrier density samples a closed FS was observed, in high carrier density superconducting Cu$_{x}$Bi$_{2}$Se$_{3}$ samples the FS was found to be open. The open FS puts constraints on the possible order-parameters in this system.