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arXiv:2609.12856

Chiral Valence-Bond Solid and Chiral Triplons

Shinnosuke Koyama, Kazumasa Hattori

Published Sep 11, 2026• 0 citations
arXivHTMLPDF

Abstract

We propose a chiral valence-bond solid (VBS) in which spin-singlet bond order itself spontaneously acquires handedness without magnetic order. Using a spin-lattice model on the diamond lattice, we demonstrate two enantiomorphic VBS states. In the presence of anisotropic spin interactions, this emergent handedness is inherited by chiral triplons with spin-split bands and spin textures that reverse between the two enantiomers. These textures generate a temperature-gradient-induced net spin response whose sign is set by the VBS handedness. The imaginary off-diagonal components of the dynamical spin structure factor encode the triplon polarization and change sign between the two enantiomers, enabling direct detection of chiral triplons and the selected handedness by polarized inelastic neutron scattering. Our results establish a direct connection between spontaneous chirality and magnetic excitations, opening avenues for exploring the interplay between quantum magnetism and chiral physics.

DOI
10.48550/arxiv.2609.12856

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We propose a chiral valence-bond solid (VBS) in which spin-singlet bond order itself spontaneously acquires handedness without magnetic order. Using a spin-lattice model on the diamond lattice, we demonstrate two enantiomorphic VBS states. In the presence of anisotropic spin interactions, this emergent handedness is inherited by chiral triplons with spin-split bands and spin textures that reverse between the two enantiomers. These textures generate a temperature-gradient-induced net spin response whose sign is set by the VBS handedness. The imaginary off-diagonal components of the dynamical spin structure factor encode the triplon polarization and change sign between the two enantiomers, enabling direct detection of chiral triplons and the selected handedness by polarized inelastic neutron scattering. Our results establish a direct connection between spontaneous chirality and magnetic excitations, opening avenues for exploring the interplay between quantum magnetism and chiral physics.
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We show that the optical responses below the Mott gap can be used to probe the spin-triplet excitations in valence bond solid (VBS) phases in Mott insulators. The optical conductivity in this regime arises due to the electronic polarization mechanism via virtual electron hopping processes. We apply this mechanism to the Hubbard model with spin-orbit couplings and/or the corresponding spin model with significant Dzyaloshinskii-Moriya (DM) interactions, and compute the optical conductivity of VBS states on both ideal and deformed Kagome lattices. In case of the deformed Kagome lattice, we study the antiferromagnet, Rb2_22​Cu3_33​SnF12_{12}12​ with the pinwheel VBS state. In case of the ideal Kagome lattice, we explore the optical conductivity signatures of the spin-triplet excitations for three VBS states with (1) a 12-site unit cell, (2) a 36-site unit cell with six-fold rotation symmetry, and (3) a 36-site unit cell with three-fold rotation symmetry, respectively. We find that increasing the DM interactions generally leads to broad and smooth features in the optical conductivity with interesting experimental consequences. The optical conductivity reflects the features of the spin-triplet excitations that can be measured in future experiments.