@@ Three-dimensional topological insulators are band insulators with gapless,Dirac-particle like surface states protected by time reversal symmetry.As a new state of matter,it holds great potential for spintronics applications and quantum computing technology.Here we report our recent magnetotransport study of Bi2Te3 films at low temperatures[1].Our Bi2Te3 films were grown along c-axis by molecular beam epitaxy on(111)semi-insulating GaAS substrates.A schematic band structure with gapless SSs is illustrated in the left inset of Fig.1(b).In the tilted MR measurement,the angle 0 between the magnetic field B and the current I Call be varied (the fight inset of Fig.1(b)).