Dresden 2017 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 1: Transport: Topological Insulators (jointly with DS, MA, HL, O)
DS 1.6: Vortrag
Montag, 20. März 2017, 10:45–11:00, HSZ 204
Ferromagnetic transition and fluctuation-induced Dzyaloshinskii-Morya interaction at the surface of three-dimensional topological insulators — •Flavio Nogueira1, Ferhat Katmis2, and Ilya Eremin2 — 1Institut für Theoretische Physik III, Ruhr-Universität Bochum — 2Deparment of Physics and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology
A ferromagnetic insulator (FMI) proximate to the surface of a three-dimensional topological insulator (TI) generate a gap in the spectrum of surface Dirac fermions, provided an out-of-plane exchange exists. We study the ferromagnetic transition in TI-FMI structures and show that fluctuations from Dirac fermions induce a Dzyaloshinskii-Morya (DM) interaction in the effective free energy of the FMI. This DM interaction arises only if the chemical potential is nonzero. Thus, if the proximity effect gaps the Dirac fermions, this means that the Fermi level must be outside the gap in order for a DM term to be induced. We also show that the Curie temperature of the ferromagnetic state at the interface between the TI and FMI is necessarily higher than the bulk Curie temperature of the FMI. This result is corroborated by recent experiments in Bi2Se3-EuS bilayer structures. These results imply an interface critical behavior very different from the bulk FMI.