Chiral Valence-Bond Solid and Chiral Triplons

Abstract

We propose a chiral valence-bond solid (VBS) state that spontaneously breaks inversion and mirror symmetries. It is characterized by a finite electric toroidal (ET) monopole, whose sign distinguishes the two enantiomorphic states. Using a spin-lattice model with Dzyaloshinskii-Moriya interactions, we show that the chiral VBS produces spin-split triplon bands with enantiomer-dependent spin textures governed by its ET monopole. Under a temperature gradient, these spin textures generate a net spin response whose sign is tied to the handedness of the VBS. More importantly, we show that the imaginary off-diagonal components of the dynamical spin structure factor change sign between the two enantiomers, providing a direct neutron-scattering probe of the selected handedness. These results establish a route to spontaneous chirality in a valence-bond system and to its direct detection through magnetic excitations.