Weak Electron-Phonon Coupling and Unusual Electron Scattering of Topological Surface States in Sb(111) by Laser-Based Angle-Resolved Photoemission Spectroscopy

High-resolution laser-based angle-resolved photoemission (ARPES) measurements are carried out on Sb(111) single crystal. Two kinds of Fermi surface sheets are observed, which are derived from the topological surface states: one small hexagonal electron-like Fermi pocket around Γ point and the other six elongated lobes of hole-like Fermi pockets around the electron pocket. Clear Rashba-type band splitting due to the strong spin-orbit coupling is observed to be anisotropic in the momentum space. Our super-high-resolution ARPES measurements reveal no obvious kink in the surface band dispersions, indicating a weak electron-phonon interaction in the surface states. In particular, the electron scattering rate for these topological surface states is nearly a constant over a large energy window near the Fermi level that is unusual in terms of the conventional picture.