Dresden 2020 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 8: Topological Phenomena (joint session MA/TT)

TT 8.2: Talk

Monday, March 16, 2020, 09:45–10:00, POT 6

Large magnetic gap at the Dirac point and spin polarization control in Bi₂Te₃/MnBi₂Te₄ heterostructures — •Friedrich Freyse¹, Emile Rienks¹, Stefan Wimmer², Andreas Ney², Hubert Steiner², Valentine Volobuev², Heiko Groiss², Günther Bauer², Andrei Varykhalov¹, Oliver Rader¹, Gunther Springholz², and Jaime Sánchez-Barriga¹ — ¹Helmholtz-Zentrum Berlin für Materialien und Energie, BESSY II, Berlin, Germany — ²Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Linz, Austria

Using spin- and angle-resolved photoemission, we investigate the electronic and spin structure of the topological surface state (TSS) of Bi₂Te₃/MnBi₂Te₄ heterostructures as a function of temperature. By cooling below the Curie temperature T_C, we observe how a magnetic surface gap opens at the Dirac point of the initially gapless TSS, a requirement which is crucial to enable the quantum anomalous Hall effect. The spectrum of the gapped Dirac point measured in remanence after field cooling (M+) is clearly spin polarized, with spin orientation perpendicular to the surface plane and spin split by a large value of Δ = 56 ± 4 meV at 6 K. Subsequent measurement at room temperature shows that the spin polarization completely disappears, whereas subsequent cooling in an oppositely oriented field (M-) leads to a reversal of the spin polarization.

[1] J.Sánchez-Barriga et al. Nature (2019), in press