Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 59: Topological Insulators II (jointly with DS, HL, O, TT)

MA 59.2: Vortrag

Freitag, 24. März 2017, 09:45–10:00, HSZ 04

Origin of Dirac cones in projected band-gaps: W(110) — •Gustav Bihlmayer¹, Andrei Varykhalov², Oliver Rader², and Stefan Blügel¹ — ¹Peter Grünberg Institut (PGI-1) & Institute for Advanced Simulation (IAS-1), Forschungszentrum Jülich and JARA, 52425 Jülich, Germany — ²Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, 12489 Berlin, Germany

Angle-resolved photoemission experiments show the existence of band-crossings with linear dispersion - often called Dirac-cones - in the projected band gaps of W(110) and Au-covered W(110). While previous studies focused on a Dirac-cone at the Γ-point and the possible connection to the topology of the bulk band-structure [1], we analyze the band-crossings in the metallic regions of the band structure along the Γ − N line of the Brillouin zone where such a term is not well defined. Based on density functional theory calculations we elucidate the origin of these crossings and find three necessary ingredients for the evolution of such structures: (i) the crossing of two surface states of different symmetry (ii) the presence of spin-orbit coupling that leads to a Rashba-type splitting of these states and (iii) mirror symmetry that protects the crossing point of the bands [2]. We discuss the relation of this mirror symmetry to the properties of topological crystalline insulators, which show similar Dirac-cones in global band-gaps.
Financial support of the DFG (SPP 1666) is gratefully acknowledged.
D. Thonig et al., Phys. Rev. B. 94, 155132 (2016).
A. Varykhalov et al., submitted (2016).