  Shubnikov-de Haas (SdH) oscillations are observed in Bi2Se3 flakes with high
carrier concentration and low bulk mobility. These oscillations probe the
protected surface states and enable us to extract their carrier concentration,
effective mass and Dingle temperature. The Fermi momentum obtained is in
agreement with angle resolved photoemission spectroscopy (ARPES) measurements
performed on crystals from the same batch. We study the behavior of the Berry
phase as a function of magnetic field. The standard theoretical considerations
fail to explain the observed behavior.
