Observation of 4- and 6-Magnon Bound States in the Spin-Anisotropic Frustrated Antiferromagnet FeI_{2}

Anaëlle Legros; Shang-Shun Zhang; Xiaojian Bai; Hao Zhang; Zhiling Dun; W Adam Phelan; Cristian D Batista; Martin Mourigal; N P Armitage

doi:10.1103/PhysRevLett.127.267201

Observation of 4- and 6-Magnon Bound States in the Spin-Anisotropic Frustrated Antiferromagnet FeI_{2}

Phys Rev Lett. 2021 Dec 24;127(26):267201. doi: 10.1103/PhysRevLett.127.267201.

Authors

Anaëlle Legros¹, Shang-Shun Zhang², Xiaojian Bai^{3

4}, Hao Zhang^{2

5}, Zhiling Dun³, W Adam Phelan⁶, Cristian D Batista², Martin Mourigal³, N P Armitage¹

Affiliations

¹ The Institute for Quantum Matter and the Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
² Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
³ School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
⁴ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁵ Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁶ PARADIM, Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.

PMID: 35029479
DOI: 10.1103/PhysRevLett.127.267201

Abstract

We observe a wealth of multimagnon bound states in the strongly anisotropic spin-1 triangular antiferromagnet FeI_{2} using time-domain terahertz spectroscopy. These unconventional excitations can arise in ordered magnets due to attractive magnon-magnon interactions and alter their properties. We analyze the energy-magnetic field spectrum via an exact diagonalization method for a dilute gas of interacting magnons and detect up to 4- and 6-magnon bound states, hybridized with single magnons. This zoo of tunable interacting quasiparticles provides a unique platform to study decay and renormalization, reminiscent of the few-body problems found in cold-atom, nuclear, and particle physics.