Strong quantum effects in an almost classical antiferromagnet on a kagome lattice

Abstract

Two ubiquitous features of frustrated spin systems stand out: massive degeneracy of their ground states and flat, or dispersionless, excitation branches. In real materials, the former is frequently lifted by secondary interactions or quantum fluctuations, in favor of an ordered or spin-liquid state, but the latter often survive. We demonstrate that flat modes may precipitate remarkably strong quantum effects even in the systems that are otherwise written off as almost entirely classical. The resultant spectral features should be reminiscent of the quasiparticle breakdown in quantum systems, only here the effect is strongly amplified by the flatness of spin-excitation branches, leading to the damping that is not vanishingly small even at $S\gg 1$. We provide a theoretical analysis of excitation spectrum of the $S=5/2$ iron-jarosite to illustrate our findings and to suggest further studies of this and other frustrated spin systems.

7 pages, accepted to PRB

References in corpus (16)

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• Frustration and Dzyaloshinsky-Moriya anisotropy in the kagome francisites Cu${}_3$Bi(SeO${}_3{)}_2$O${}_2$X
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• Decay of quasiparticles in quantum spin liquids
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Cited by in corpus (17)

• Magnon thermal Hall effect in kagome antiferromagnets with Dzyaloshinskii-Moriya interactions
• Interaction-stabilized topological magnon insulator in ferromagnets
• Intrinsic spin Nernst effect of magnons in a noncollinear antiferromagnet
• Order and excitations in large-$S$ kagomé-lattice antiferromagnets
• Topological Phases in Magnonics
• Magnon damping in the zigzag phase of the Kitaev-Heisenberg-$\Gamma$ model on a honeycomb lattice
• Generic nearest-neighbour kagome model: XYZ & Dzyaloshinskii-Moriya, and comparison to pyrochlore
• Field-induced dynamical properties of the $XXZ$ model on a honeycomb lattice
• Emergent Potts order in the kagomé $J_1-J_3$ Heisenberg model
• Magnon Hall Effect without Dzyaloshinskii-Moriya Interaction
• Quantum Damping of Skyrmion Crystal Eigenmodes due to Spontaneous Quasiparticle Decay
• Magnon interactions in the quantum paramagnetic phase of CoNb${}_2$O${}_6$
• Structures of magnetic excitations in the spin-1/2 kagome-lattice antiferromagnets Cs${}_2$Cu${}_3$SnF${}_{12}$ and Rb${}_2$Cu${}_3$SnF${}_{12}$
• Breakdown of Linear Spin-wave Theory and Existence of Spinon Bound States in the Frustrated Kagome Lattice Antiferromagnet
• Effects of magnon-magnon interactions in a noncollinear magnet induced by combination of a symmetric and an antisymmetric exchange interaction
• High-Field Expansion Approach to Kagome Antiferromagnets with Dzyaloshinskii-Moriya Interactions
• Is Herbertsmithite far from an ideal antiferromagnet? Ab-initio answer including in-plane Dzyaloshinskii-Moriya interactions and coupling with extra-plane impurities