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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)

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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