A. A. Taskin, Satoshi Sasaki, Kouji Segawa, Yoichi Ando
The massless Dirac fermions residing in the surface of topological insulators are protected from backscattering and cannot be localized by disorder, but such a protection can be lifted by a topological phase transition. By measuring the Shubnikov-de Haas oscillations in a series of high-quality Bi2Se3 thin films, we revealed a systematic evolution of the surface conductance as a function of thickness and found a striking manifestation of the topological phase transition: The metallic surface transport abruptly diminished below the critical thickness of ~6 nm, at which an energy gap opens in the surface state and the Dirac fermions become massive. This transition is also manifested in the weak antilocalization behavior, which weakens in the gapped phase due to the loss of \pi Berry phase.
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http://arxiv.org/abs/1204.1829
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