Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 4: Topological Insulators 1 (jointly with DS, HL, MA, and O)
TT 4.3: Talk
Monday, March 11, 2013, 10:15–10:30, H10
Investigation of the relation between surface band gaps and magnetism in the magnetic topological insulator (Bi1−xMnx)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 (Bi1−xMnx)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.