Weyl-triplons in SrCu2(BO3)2

Abstract

We propose that Weyl triplons are expected to appear in the low energy magnetic excitations in the canonical Shastry-Sutherland compound, \ce{SrCu2(BO3)2}, a quasi-2D quantum magnet. Our results show that when a minimal, realistic inter-layer coupling is added to the well-established microscopic model describing the excitation spectrum of the individual layers, the Dirac points that appear in the zero-field triplon spectrum of the 2D model split into two pairs of Weyl points along the $k_z$ direction. Varying the strength of the inter-layer DM-interaction and applying a small longitudinal magnetic field results in a range of band-topological transitions accompanied by changing numbers of Weyl points. We propose inelastic neutron scattering along with thermal Hall effect as the experimental techniques to detect the presence of Weyl node in the triplon spectrum of this material. We show that the logarithmic divergence in the second derivative in thermal Hall conductance near phase transition from regime Weyl points to a regime with topologically gapped bands as well as a finite slope in the thermal Hall conductance as a function of magnetic field at zero magnetic field are promising evidence for the presence of Weyl triplons.

13 pages, 6 figures

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• Magnon Hall effect in antiferromagnetic lattices
• Tuning bulk topological magnon properties with light-induced magnons
• Formulation of spin Nernst effect for spin-nonconserving insulating magnets
• Spin Nernst and thermal Hall effects of topological triplons in quantum dimer magnets on the maple-leaf and star lattices
• Scattering Theory of Chiral Edge Modes in Topological Magnon Insulators
• Stabilization of Granovskii-Zhedanov scars of the XYZ quantum spin chain via non-Hermitian spin relaxation
• Intrinsic suppression of topological thermal Hall effect in an exactly solvable quantum magnet