Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 7: Spin-Orbit Interaction at Surfaces I

O 7.4: Vortrag

Montag, 22. März 2010, 12:00–12:15, H38

Spin-polarized topological surface states of topological insulators Bi₂Te₃ and Bi₂Se₃ — •Markus R. Scholz¹, Dmitry Marchenko¹, Andrei Varykhalov¹, Oliver Rader¹, Andrey Volykhov², and Lada V. Yashina² — ¹Helmholtz-Zentrum Berlin für Materialien und Energie — ²Department of Chemistry, Moscow State University

The topological insulator has been proposed as new state of quantum matter in 2005 [1]. A gap in the two-dimensional bulk is crossed by one-dimensional states which occur as pairs in which the spin of each partner is connected to its propagation direction. A generalization towards three-dimensional solids predicted topological insulator properties for Bi10%Sb and Bi₂Te₃ [2]. Spin resolution is crucial for distinguishing the topological from ordinary surface states in experiment as was shown for Bi10%Sb [3]. For Bi₂Te₃ only spin-averaged data exists [4]. We grew Bi₂Te₃ and Bi₂Se₃ single crystals by the Bridgeman method and conducted spin- and angle-resolved photoemission. For both systems, the spin-resolved spectra show that the surface state forms a single non-degenerate Dirac cone with the Kramers degeneracy point at Γ. Spin- and angle-resolved spectra above and below the Kramers point and for positive and negative k_∥ clearly show the spin-momentum relation expected for the surface of a topological insulator.

[1] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 146802 (2005); 226801 (2005) [2] L. Fu and C. L. Kane, Phys. Rev. 76, 045302 (2007) [3] D. Hsieh et al., Science 323, 920 (2009) [4] Y. Xia et al., Nature Phys. 5, 398 (2009)