Non-linear magnons and exchange Hamiltonians of delafossite proximate quantum spin liquids

Abstract

Quantum spin liquids (QSL) are theoretical states of matter with long-range entanglement and exotic quasiparticles. However, they generally elude quantitative theory, rendering their underlying phases mysterious and hampering efforts to identify experimental QSL states. Here we study triangular lattice resonating valence bond QSL candidate materials KYbSe${}_2$ and NaYbSe${}_2$. We measure the magnon modes in their 1/3 plateau phase, where quantitative theory is tractable, using inelastic neutron scattering and fit them using nonlinear spin wave theory. We also fit the KYbSe${}_2$ heat capacity using high temperature series expansion. Both KYbSe${}_2$ fits yield the same magnetic Hamiltonian to within uncertainty, confirming previous estimates and showing the Heisenberg $J_2/J_1$ to be an accurate model for these materials. Most importantly, comparing KYbSe${}_2$ and NaYbSe${}_2$ shows that smaller $A$-site Na${}^{+}$ ion has a larger $J_2/J_1$ ratio. However, hydrostatic pressure applied to KYbSe${}_2$ increases the ordering temperature (a result consistent with density functional theory calculations), indicating that pressure decreases $J_2/J_1$. These results show how periodic table and hydrostatic pressure can tune the $A$YbSe${}_2$ materials in a controlled way.

7 pages, 7 figures; 4 pages and 7 additional figures of supplemental information

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Cited by in corpus (18)

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• Continuum of spin excitations in an ordered magnet
• Rare-Earth Chalcogenides: An Inspiring Playground For Exploring Frustrated Magnetism
• Phase diagram of the quantum spin-1/2 Heisenberg-$\Gamma$ model on a frustrated zigzag chain
• Anomalous continuum scattering and higher-order van Hove singularity in the strongly anisotropic S = 1/2 triangular lattice antiferromagnet
• Quantum and classical spin dynamics across temperature scales in the S = 1/2 Heisenberg antiferromagnet
• Classical dynamics of the antiferromagnetic Heisenberg $S=1/2$ spin ladder
• Field-driven transition from quantum spin liquid to magnetic order in triangular-lattice antiferromagnets
• The Finite-Temperature Behavior of a Triangular Heisenberg Antiferromagnet
• Random singlet physics in exchange disordered 2D triangular YbCu${}_{1.14}$Se${}_2$
• Derivation of low-energy Hamiltonians for heavy-fermion Materials
• Competing states in the $S=1/2$ triangular-lattice $J_1$-$J_2$ Heisenberg model: a dynamical density-matrix renormalization group study
• 5d-mediated indirect exchange and effective spin Hamiltonians in Ce triangular-lattice delafossites
• Finite Spinon Density-of-States in Triangular-Lattice Delafossite TlYbSe${}_2$
• Magnetic ground state of a Jeff = 1/2 based frustrated triangular lattice antiferromagnet
• Specific heat and susceptibility of S=1/2 antiferromagnets on square, triangular, and kagome lattices