Observation of Superparamagnetism in Coexistence with Quantum Anomalous Hall C=±1 and C=0 Chern States

ORAL

Abstract

Simultaneous transport and scanning nanoSQUID-on-tip magnetic imaging studies in Cr-(Bi,Sb)2Te3 modulation-doped films reveal the presence of superparamagnetic (SPM) order within the quantum anomalous Hall (QAH) regime. SPM dynamics of weakly interacting nanoscale magnetic islands is observed both in the transition regions as well as within the fully quantized C=±1 Chern plateaus. Modulation doping of the topological insulator films is found to give rise to significantly larger SPM islands as compared to uniform magnetic doping, evidently leading to enhanced robustness of the QAH effect. Even in this more robust quantum state, attaining full quantization of transport coefficients requires magnetic alignment of at least 95% of the SPM islands.
The SPM order is also found within the incipient C=0 zero Hall plateau, which may host an axion state if top and bottom layers are magnetized in opposite directions. In this regime, however, a lower level of island alignment is found, hindering the formation of the axion state. Comprehension and control of SPM dynamics is thus a key factor in apprehending the fragility of the QAH state.
[arXiv:1710.06446]

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Presenters

  • Ella Lachman

    Department of Physics, Univ of California - Berkeley

Authors

  • Ella Lachman

    Department of Physics, Univ of California - Berkeley

  • Masataka Mogi

    Univ of Tokyo, Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Applied Physics, University of Tokyo

  • Jayanta Sarkar

    Department of Condensed Matter Physics, Weizmann Institute of Science

  • Aviram Uri

    Department of Condensed Matter Physics, Weizmann Institute of Science

  • Kousik Bagani

    Department of Condensed Matter Physics, Weizmann Institute of Science

  • Yonathan Anahory

    The Hebrew University of Jerusalem, Racah Institute of Physics, The Hebrew University

  • Yuri Myasoedov

    Department of Condensed Matter Physics, Weizmann Institute of Science

  • Martin Huber

    Department of Physics, University of Colorado Denver, Physics, University of Colorado Denver

  • Atsushi Tsukazaki

    Institute for Materials Reaserch, Tohoku University, Tohoku Univ, Institute for Materials Research, Tohoku University, IMR, Tohoku University, Institute for Materials Research, Tohoku University, Tohoku Univ.

  • Masashi Kawasaki

    Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), the University of Tokyo, Univ of Tokyo, The University of Tokyo, Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), Univ. of Tokyo, Applied Physics, University of Tokyo, Department of Applied Physics, The University of Tokyo, Department of Applied Physics, University of Tokyo

  • Yoshinori Tokura

    RIKEN Center for Emergent Matter Science (CEMS), CEMS, RIKEN, RIKEN, Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, RIKEN Center for Emergent Matter Science, Center for Emergent Matter Science (CEMS), RIKEN, Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo

  • Eli Zeldov

    Department of Condensed Matter Physics, Weizmann Institute of Science, Weizmann Institute of Science