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Spin Dynamics and Dirac Nodes in a Kagome Lattice
Author(s) -
Boyko Daniel,
Saxena Avadh,
Haraldsen Jason T.
Publication year - 2020
Publication title -
annalen der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.009
H-Index - 68
eISSN - 1521-3889
pISSN - 0003-3804
DOI - 10.1002/andp.201900350
Subject(s) - physics , condensed matter physics , antiferromagnetism , anisotropy , hamiltonian (control theory) , ferromagnetism , lattice (music) , isotropy , frustration , magnetic field , hexagonal lattice , quantum mechanics , mathematical optimization , mathematics , acoustics
Herein, the spin dynamics for various magnetic configurations arranged on a Kagome lattice is investigated. Using a Holstein–Primakoff expansion of the isotropic Heisenberg Hamiltonian with multiple exchange parameters, the development and evolution of magnetic Dirac nodes with both anisotropy and magnetic field are examined. From the classical energies, the phase diagrams for the ferromagnetic (FM), antiferrimagnetic (AfM), and the 120° phases are shown as functions of J 1 , J 2 , J 3 , and anisotropy. Furthermore, the production of bosonic Dirac and Weyl nodes in the spin‐wave spectra is shown. Through frustration of the magnetic geometry, a connection to the asymmetric properties of the Kagome lattice and the various antiferromagnetic configurations is discerned. Most interesting is the 120° phase, which does not have Dirac nodes when considering only J 1 due to the formation of an analogous antiferromagnetic honeycomb lattice, but gains Dirac symmetry with next‐nearest neighbor interactions. Additionally, the presence of flat modes that are characteristic of cluster excitations is shown. Further study of external frustrations from a magnetic field and anisotropy reveals a tunability of the exchange interactions and nodal points.