Regensburg 2022 – wissenschaftliches Programm
KFM 28.2: Vortrag
Donnerstag, 8. September 2022, 15:30–15:45, H37
Tuning the magnetic gap of a topological insulator — •Marcus Liebmann1, Philipp Küppers1, Jannik Zenner1, Stefan Wimmer2, Gunther Springholz2, Oliver Rader3, and Markus Morgenstern1 — 1II. Phys. Inst. B, RWTH Aachen Univ., Germany — 2Inst. Halbleiter- u. Festkörperphysik, Johannes Kepler Univ., Linz, Austria — 3Helmholtz-Zentrum Berlin f. Mater. u. Energie, Germany
Mn-rich MnSb2Te4 is a ferromagnetic topological insulator with yet the highest Curie temperature TC = 45−50 K. It exhibits a magnetic gap at the Dirac point of the topological surface state that disappears above TC. We probe the gap size by scanning tunneling spectroscopy, varying in-plane magnetic field B|| and temperature. We demonstrate shrinkage of the average gap size with B|| revealing that the gap opening originates from out-of-plane magnetization. In line, the gap does not close completely up to B|| = 3 T as the magnetization is only partially rotated in-plane. In addition, we demonstrate significant spatiotemporal fluctuations of the gap size at temperatures as low as TC/2, above which the remanent magnetization indeed decays. Thus, the gap is tightly bound to the out-of-plane magnetization, as expected theoretically but not demonstrated experimentally yet. The partial in-plane rotation at B|| = 3 T and the low temperature onset of fluctuations stress the important role of competing magnetic orders in the formation of the favorable ferromagnetic topological insulator in Mn-rich MnSb2Te4, providing insight into the complex magnetic gap opening that is decisive for quantum anomalous Hall devices.