Observation of high order multi-magnon (<i>n</i> = 4 and 6) bound states in the frustrated triangular antiferromagnetic lattice FeI<sub>2</sub>

ORAL

Abstract

Spin waves (e.g. magnons) are the conventional elementary excitations of a magnetically ordered phase. However, other possibilities exist. For instance, magnon bound states can arise at low energy due to attractive magnon-magnon interactions and modify the low-temperature properties of the system. The most common case corresponds to two-magnon bound states (n = 2) in quasi-one-dimensional quantum magnets [1]. Here we study the frustrated spin-1 triangular antiferromagnetic lattice FeI2 [2] using time-domain terahertz spectroscopy. The spectra reveal a zoo of distinct multi-magnon quasiparticles at low energies, including up to six-magnon bound states, along with interactions between them. The energy-magnetic field excitation spectrum provides valuable information on the Hamiltonian of this peculiar material and is well reproduced by exact diagonalization calculations of a low-energy Hamiltonian for a dilute gas of interacting quasiparticles. The existence of these high order magnon bound states provides a novel platform to study multiparticle interactions and decays in a condensed matter setting.

[1] Torrance and Tinkham, Phys. Rev. 187, 595 (1969)
[2] Bai et al., arXiv:2004.05623 (2020)

*Supported by the Institute for Quantum Matter under DOE EFRC grant DE-SC0019331.

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Presenters

  • Anaelle Legros

    • Johns Hopkins University
    • Universite de Sherbrooke
    • Université de Sherbrooke

Authors

  • Anaelle Legros

    • Johns Hopkins University
    • Universite de Sherbrooke
    • Université de Sherbrooke

  • Shang-Shun Zhang

    • University of Tennessee
    • School of Physics and Astronomy, University of Minnesota
    • Department of Physics and Astronomy, University of Tennessee, Knoxville
    • University of Minnesota

  • Xiaojian Bai

    • Georgia Institute of Technology
    • School of Physics, Georgia Institute of Technology

  • Hao Zhang

    • University of Tennessee
    • Department of Physics and Astronomy, University of Tennessee
    • Department of Physics and astronomy, University of Tennessee
    • Department of Physics and Astronomy, University of Tennessee, Knoxville
    • Department of Materials Science, The University of Tennessee

  • Cristian Batista

    • University of Tennessee
    • Department of Physics & Astronomy, University of Tennessee, Knoxville, TN 37996, USA
    • Department of Physics and Astronomy, University of Tennessee
    • Physics and Astronomy, University of Tennessee
    • Oakridge National Laboratory
    • Department of Physics and astronomy, University of Tennessee
    • University of Tennessee, Knoxville
    • Department of Physics and Astronomy, University of Tennessee, Knoxville

  • Martin P Mourigal

    • Georgia Institute of Technology
    • Georgia Inst of Tech
    • School of Physics, Georgia Institute of Technology

  • Peter Armitage

    • Johns Hopkins University
    • Department of Physics and Astronomy, Johns Hopkins University, Baltimore 21218
    • Department of Physics and Astronomy, Johns Hopkins University