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Gaku Eguchi, K. Kuroda, A. Kimura, M. Shiraishi:
"Transport Properties of the Ideal Surface Dirac Cone in the Topological Insulator Tl1-xBi1+xSe2";
Vortrag: New Trends in Topological Insulators 2015, Donostia-San Sebastian; 06.07.2015 - 10.07.2015.

Surface Dirac fermion system of the three-dimensional (3D) topological insulators exhibits a spin-momentum locked electronic state, and the system is understood as a new stage of novel electric- and spin-transport [1]. A number of new topological insulators have been discovered for the past few years. However, most of them turned out to exhibit bulk metallic conduction and the novel surface transport phenomena were hidden in the bulk conduction.
TlBiSe2 is not only a 3D topological insulator exhibiting a large bulk band gap, but also reported as a bulk metal [1]. Recently, considerable amount of electron doping due to the sample defect was revealed, and by controlling the defect bulk-insulating state was realized [2]. This is the first demonstration other than the Bi2Se3-based topological insulators, and the achievement opens the new stage of researches for the novel surface transport. More importantly, the surface Dirac cone exhibits a
simple structure, i.e., the in-gap Dirac point and a small in-plane distortion. These facts indicate that the bulk-insulating TlBiSe2 is the ideal stage for studies of surface transport.
In this presentation we report the electric transport properties of the TlBiSe2 of both bulk insulating and bulk metallic samples. The two-dimensional Shubnikov-de Haas oscillations in a bulk- insulating sample were observed. Landau level- fan diagram of the oscillation showed the π Berry phase (see Figure 1), and the fact indicated that the oscillations were originated from the surface Dirac fermions. Mobility of both surface and bulk were determined, and compared with each other. We present our recent data and discuss scattering mechanisms.