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Ultrafast momentum-resolved study of electron-phonon coupling in an antiferromagnetic topological insulator

ORAL

Abstract

Elementary electronic and lattice excitations and their mutual interactions form the foundation of our understanding of condensed matter systems. In the context of topological insulators, the electron-phonon coupling determines in addition, the robustness of dissipationless surface states at finite temperatures. In this work, we consider the first discovered intrinsic antiferromagnetic topological insulator, MnBi2Te4, a system that is predicted to exhibit the quantum anomalous Hall effect [1]. We study the momentum-resolved electron-phonon coupling in this material at its inherent femtosecond timescale using ultrafast electron diffraction and coherent phonon optical spectroscopy. We find that electrons are strongly coupled to in-plane zone-boundary Eg optical phonons, resulting in a highly nonequilibrium phonon population for several hundreds of femtoseconds after excitation. The nonequilibrium phonon system subsequently relaxes by phonon-phonon coupling to zone-center transverse acoustic phonons. We simulate how the strongly coupled Eg phonons modulate the exchange interaction and magnetism using DFT calculations.

[1] J. Li, Y. Li, S. Du, Z. Wang, B.-L. Gu, S.-C. Zhang, K. He, W. Duan, and Y. Xu, Sci. Adv. 5, eaaw5685 (2019).

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Presenters

  • Haricharan Padmanabhan

    Pennsylvania State University

Authors

  • Haricharan Padmanabhan

    Pennsylvania State University

  • Vladimir A Stoica

    Pennsylvania State University

  • Huaiyu Wang

    Department of Materials Science and Engineering, The Pennsylvania State University, Pennsylvania State University

  • Nathan Koocher

    Northwestern University, Materials Science and Engineering, Northwestern University

  • Mingqiang Gu

    Northwestern University

  • Xiaozhe Shen

    SLAC - Natl Accelerator Lab, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA, SLAC National Accelerator Laboratory

  • Ming-Fu Lin

    SLAC National Accelerator Laboratory

  • Seng Huat Lee

    2D Crystal Consortium, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA, Physics, The Pennsylvania State University, Pennsylvania State University, MRI, Penn State University

  • Zhiqiang Mao

    Pennsylvania State University, Tulane University, Physics, Pennsylvania State University, Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA, Physics, The Pennsylvania State University, Department of Physics, Pennsylvania State University, Penn State University, Physics, Penn State University, The Pennsylvania State University

  • Aaron Lindenberg

    Stanford Univ, Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, SLAC National Accelerator Laboratory

  • Xijie Wang

    SLAC - Natl Accelerator Lab, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA, SLAC National Accelerator Laboratory

  • James Rondinelli

    Northwestern University, Department of Materials Science and Engineering, Northwestern University, Materials Science and Engineering, Northwestern University, Deparment of Materials Science and Engineering, Northwestern University

  • Venkatraman Gopalan

    Materials Science and Engineering, Pennsylvania State University, Pennsylvania State University, Materials Science and Engineering, Penn State University