Change-over of carrier type and magneto-transport property in Cu doped   Bi2Te3 Topological Insulators
  Structural, resistivity, thermoelectric power and magneto-transport properties of Cu doped Bi2Te3 topological insulators have been investigated. The occurrence of the tuning of charge carriers from n type to p type by Cu doping at Te sites of Bi2Te3 is observed both from Hall effect and thermoelectric power measurements. Carrier mobility decreases with the doping of Cu which provides evidence of the movement of Fermi level from bulk conduction band to the bulk valence band. Thermoelectric power also increaseswith doping of Cu.Moreover linear magnetoresistance (LMR) has been observed at high magnetic field in pure Bi2Te3 which is associated to the gapless topological surface states protected by time reversal symmetry (TRS), whereas doping of Cu breaks TRS and an opening of band gap occurs which quenches the LMR. 
Abhishek Singh, Rahul Singh, A. Lakhani, T. Patel, G. S. Okram, V.   Ganeshan, A. K. Ghosh and Sandip Chatterjee
cond-mat.mtrl-sci