Helimagnons in a chiral ground state of the pyrochlore antiferromagnets

Abstract

The Goldstone mode in a helical magnetic phase, also known as the helimagnon, is a propagating mode with a highly anisotropic dispersion relation. Here we study theoretically the helimagnon excitations in a complex chiral ground state of pyrochlore antiferromagnets such as spinel CdCr2O4 and itinerant magnet YMn2. We show that the effective theory of the soft modes in the helical state possesses a symmetry similar to that of smectic liquid crystals. We compute the low-energy spin-wave spectrum based on a microscopic spin Hamiltonian and find a dispersion relation characteristic of the helimagnons. By performing dynamics simulations with realistic model parameters, we also obtain an overall agreement between experiment and the numerical spin-wave spectrum. Our work thus also clarifies the mechanisms that relive the magnetic frustration in these compounds.

arXiv comment5 pages, 3 figures

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Cited by in corpus (3)

• Magnetic structure and excitation spectrum of the hyperhoneycomb Kitaev magnet $\beta$-Li${}_2$IrO${}_3$
• Exciton-magnon transitions in the frustrated chromium antiferromagnets CuCrO2, alpha-CaCr2O4, CdCr2O4, and ZnCr2O4
• Unconventional magnetic field response of the hyperhoneycomb Kitaev magnet $\beta -{\text{Li}}_2{\text{IrO}}_3$