Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 85: Topological Insulators 2 (MA with HL/TT)

HL 85.3: Talk

Thursday, March 19, 2015, 15:30–15:45, EB 202

Indirect exchange interaction through topological surface states in crystalline topological insulators of a SnTe class — •Nicolas Klier, Sam Shallcross, and Oleg Pankratov — Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7B2, 91058 Erlangen

As predicted theoretically [1,2] and confirmed experimentally [2,3] the interface of SnTe and vacuum (i.e. the material’s surface) hosts topologically stable Dirac states. We investigate the properties of this state within a k.p model that includes a full account of the bulk band structure [4]. An essential advantage of an analytical band model [4] is that it allows to unequivocally trace the two key degrees of freedom that this system possesses: spin and pseudospin. The indirect exchange interaction between magnetic impurities is a perfect probe for the surface Dirac states, especially for their spin structure. We revealed explicitly the dependence of this interaction on the properties of the bulk band states, in particular on the spin orbit coupling strength and on the crystal field splitting parameters. Depending on these parameters, the interaction may be either of Ising type or of a novel anisotropic XY type with the spin direction aligned with the connection vector between the two impurities.

[1] B.A. Volkov, and O.A. Pankratov, JETP Lett. 42, 178, 1985.

[2] T.H. Hsieh et al., Nature Comm. 3, 982, 2012.

[3] Y. Tanaka et al., Nature Phys. 8, 800, 2012.

[4] B.A. Volkov, and O.A. Pankratov, Zh.Eksp. Theor. Fiz. 75, 1362, 1978.