Wannier states and spin supersolid physics in the triangular antiferromagnet K${}_2$Co(SeO${}_3$)${}_2$

Abstract

We combine ultra-high-resolution inelastic neutron scattering and quantum Monte Carlo simulations to study thermodynamics and spin excitations in the spin-supersolid phase of the triangular lattice XXZ antiferromagnet K${}_2$Co(SeO${}_3$)${}_2$ under zero and non-zero magnetic field. BKT transitions signaling the onset of Ising and supersolid order are clearly identified, and the Wannier entropy is experimentally recovered just above the supersolid phase. At low temperatures, with an experimental resolution of about 23 $\mu$eV, no discrete coherent magnon modes are resolved within a broad scattering continuum. Alongside gapless excitations, a pseudo-Goldstone mode with a 0.06 meV gap is observed. A second, higher-energy continuum replaces single-spin-flip excitations of the Ising model. Under applied fields, the continuum evolves into coherent spin waves, with Goldstone and pseudo-Goldstone sectors responding differently. The experiments and simulations show excellent quantitative agreement.

18 + 6 pages, 18 + 5 figures

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Cited by in corpus (9)

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• Dissipationless dynamics of spin supersolid states in a spin-1/2 triangular antiferromagnet with impurities
• Nontrivial three-sublattice magnetization in the easy-axis spin-1/2 XXZ antiferromagnet on the triangular lattice
• Non-linear spin wave theory in the strong easy-axis limit of the triangular XXZ model
• The anisotropic Heisenberg model close to the Ising limit: triangular lattice vs. effective models
• Canted ferromagnetic order in a distorted triangular-lattice magnet Na${}_2$SrCo(VO${}_4$)${}_2$
• Unconventional Spin Dynamics and Supersolid Excitations in the Triangular-Lattice XXZ Model