Evidence for topological surface states in metallic single crystals of Bi₂Te₃

Bi2Te3 is a member of a new class of materials known as topological insulators which are supposed to be insulating in the interior and conducting on the surface. However, experimental verification of the conductive qualities of the surface states has been hindered by parallel bulk conductions. We report low temperature magnetotransport measurements on single crystal samples of Bi2Te3. We observe metallic character in our samples and large and linear magnetoresistance from 1.5 K to 290 K with prominent Shubnikov-de Haas (SdH) oscillations whose traces persist up to 20 K. Even though our samples are metallic, we are able to obtain a Berry phase close to the value of π, which is expected for Dirac fermions of the topological surface states. This indicates that we have obtained evidence for the topological surface states in metallic single crystals of Bi2Te3. Other physical measurements obtained from the analysis of the SdH oscillations are also in close agreement with those reported for the topological surface states. The linear magnetoresistance observed in our sample, which is considered as a signature of the Dirac fermions of the surface states, lends further credence to the existence of topological surface states.