Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 109: Tribology and Structure of Surfaces: Misc.

O 109.1: Hauptvortrag

Freitag, 24. März 2017, 10:30–11:00, WIL A317

Discovery of 1D spin-polarized states at step edges of topological crystalline insulators — •Paolo Sessi — Universität Würzburg

Topological crystalline insulators (TCIs) are topological materials where the existence of surface Dirac states is guaranteed by crystal symmetries. This protection mechanism promises a rich phenomenology in response to crystal perturbations. In my presentation, I will report on the discovery of robust 1D spin-polarized channels naturally emerging at TCI surfaces once translational invariance is broken [1]. I will illustrate how 1D channels can be easily obtained in the prototypical TCI Pb_1−xSn_xSe without the need of any sophisticated preparation technique. In particular, by correlating topographic and electronic structure information, I will show that 1D states naturally emerge at step edges consisting of an odd number of atomic layers, where translational invariance is broken, while even step edges maintain translational symmetry and are featureless. By systematically acting on the crystals stoichiometry, I will demonstrate how these 1D states are directly linked to the existence of a topologically non-trivial bulk band structure. A minimal toy model and realistic tight-binding calculations allow to identify them as spin-polarized at bands connecting two Dirac points. Finally, I will show how, contrary to 1D topological states known so far, their protection mechanisms result in a striking robustness to defects, strong magnetic fields, and elevated temperature.

[1] P. Sessi et al., Science in press.