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O: Fachverband Oberflächenphysik

O 2: Topological Insulators 1 (jointly with DS, HL, MA, TT)

O 2.3: Vortrag

Montag, 11. März 2013, 10:15–10:30, H10

Investigation of the relation between surface band gaps and magnetism in the magnetic topological insulator (Bi_1−xMn_x)₂Se₃ — •Jaime Sánchez-Barriga¹, Andrei Varykhalov¹, Gunther Springholz², Hubert Steiner², Raimund Kirchschlager², Günther Bauer², Ondrei Caha³, Enrico Schierle¹, Eugen Weschke¹, Akin Ünal¹, Sergio Valencia¹, Florian Kronast¹, and Oliver Rader¹ — ¹Helmholtz-Zentrum Berlin — ²Johannes Kepler Universität Linz — ³Masaryk University, Brno

The Dirac cone at the surface of a magnetic topological insulator is expected to open a band gap when ferromagnetically magnetized perpendicularly to the surface plane. Angle-resolved photoemission from epitaxial films of (Bi_1−xMn_x)₂Se₃ shows for x > 0.02 a band gap at the Dirac point of a size that varies with Mn concentration, is much larger than theoretically predicted (∼100 meV), and does not change with temperature from 7 to 300 K. Based on our measurements with x-ray magnetic circular dichroism (XMCD) we can exclude that the surface band gap is due to ferromagnetic order in the bulk or at the surface. In addition, we investigate by XMCD in photoemission microscopy the reported proximity magnetization induced by a ferromagnetic overlayer.