Phonon vibration modes of layered MnBi<sub>2n</sub>Te<sub>3n+1</sub> (n=1,2,3,4) topological heterostructures

ORAL

Abstract

MnBi2Te4 is the first experimentally demonstrated intrinsic antiferromagnetic topological insulator, whose properties are tunable with additional Bi2Te3 layers between adjacent MnBi2Te4 layers. In this talk, we present the phonon modes of bulk MnBi2nTe3n+1 (n=1,2,3,4) at various temperatures and polarization configurations, using optical Raman spectroscopy. Our density functional theory calculation shows that the peaks at 66 cm-1 and 112 cm-1 are mainly generated by oscillating Mn-Te chains. In MnTe2Te4, below the transition temperature, we observed an abnormal change of those two peaks due to spin-phonon coupling. In MnBi4Te7, the additional Bi2Te3 induces Davydov splitting of the A1g mode at 136 cm-1 at room temperature. From the linear chain model, we estimated the out-of-plane interlayer force constant to be 4.48×1019 N/m3, 75% weaker than that of Bi2Te3. As the number of Bi2Te3 layer increases, the Raman spectrum is dominated by the vibrational modes in Bi2Te3. Our work provides useful guidance to tailoring their physical properties in future research.

*A portion of this research was performed at the CNMS user facility at ORNL. We acknowledge NSF grant TAQS-1936375 (UCLA) and the computational resources of the CADES at the ORNL, Contract No. DE-AC05-00OR22725.

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Presenters

  • Yujin Cho

    • University of California, Los Angeles

Authors

  • Yujin Cho

    • University of California, Los Angeles

  • Jin Ho Kang

    • University of California, Los Angeles

  • Liangbo Liang

    • Oak Ridge National Laboratory
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory

  • Alexander Puretzky

    • Oak Ridge National Laboratory

  • Xiangru Kong

    • Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Subhajit Ghosh

    • University of California, Riverside

  • Fariborz Kargar

    • University of California, Riverside

  • Chaowei Hu

    • University of California, Los Angeles
    • Physics, University of California, Los Angeles
    • Physics and Astronomy Department, University of California, Los Angeles
    • Department of Physics and Astronomy, University of California, Los Angeles

  • Ni Ni

    • University of California, Los Angeles
    • Physics, University of California, Los Angeles
    • Physics and Astronomy Department, University of California, Los Angeles
    • Department of Physics and Astronomy, University of California, Los Angeles

  • Alexander A Balandin

    • University of California, Riverside

  • David B Geohegan

    • Oak Ridge National Laboratory

  • Chee Wei Wong

    • Electrical & Computer Engineering and Center for Quantum Science & Engineering, University of California, Los Angeles
    • Fang Lu Mesoscopic Optics and Quantum Electronics Laboratory, University of California, Los Angeles
    • University of California, Los Angeles
    • University of California Los Angeles
    • UCLA Foundation