Dynamical dimer structure factor of the triangular $S=1/2$ Heisenberg antiferromagnet

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Main Authors: Drescher, Markus, Vanderstraeten, Laurens, Moessner, Roderich, Pollmann, Frank, Knolle, Johannes
Format: Preprint
Published: 2026
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author Drescher, Markus
Vanderstraeten, Laurens
Moessner, Roderich
Pollmann, Frank
Knolle, Johannes
author_facet Drescher, Markus
Vanderstraeten, Laurens
Moessner, Roderich
Pollmann, Frank
Knolle, Johannes
contents The dynamical dimer structure factor is an observable probing spin-singlet excitations of quantum magnets distinct from those commonly studied by the spin structure factor. We report the dimer response for the extended spin-$1/2$ antiferromagnetic Heisenberg model on the triangular lattice using large-scale GPU-accelerated matrix-product-state simulations. We investigate the ordered phases with $120^\circ$ coplanar, collinear stripe, and tetrahedral spin order, as well as candidate quantum spin-liquid (QSL) regimes, comprising an expected gapless $U(1)$ Dirac QSL and a chiral QSL at finite spin-scalar-chirality coupling. In the ordered phases, we find low-energy modes below the onset of the two-magnon continuum illustrating avoided quasiparticle decay. Within the candidate gapless QSL, we observe absolute dispersion minima at momenta of half the Brillouin zone corners, $X\equiv K/2$, in agreement with field-theory predictions that singlet monopole excitations of the $U(1)$ Dirac spin liquid become gapless at these points. Thus, the high-resolution dynamical dimer response provides support for a $U(1)$ Dirac QSL with singlet monopole excitations.
format Preprint
id arxiv_https___arxiv_org_abs_2604_24868
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Dynamical dimer structure factor of the triangular $S=1/2$ Heisenberg antiferromagnet
Drescher, Markus
Vanderstraeten, Laurens
Moessner, Roderich
Pollmann, Frank
Knolle, Johannes
Strongly Correlated Electrons
The dynamical dimer structure factor is an observable probing spin-singlet excitations of quantum magnets distinct from those commonly studied by the spin structure factor. We report the dimer response for the extended spin-$1/2$ antiferromagnetic Heisenberg model on the triangular lattice using large-scale GPU-accelerated matrix-product-state simulations. We investigate the ordered phases with $120^\circ$ coplanar, collinear stripe, and tetrahedral spin order, as well as candidate quantum spin-liquid (QSL) regimes, comprising an expected gapless $U(1)$ Dirac QSL and a chiral QSL at finite spin-scalar-chirality coupling. In the ordered phases, we find low-energy modes below the onset of the two-magnon continuum illustrating avoided quasiparticle decay. Within the candidate gapless QSL, we observe absolute dispersion minima at momenta of half the Brillouin zone corners, $X\equiv K/2$, in agreement with field-theory predictions that singlet monopole excitations of the $U(1)$ Dirac spin liquid become gapless at these points. Thus, the high-resolution dynamical dimer response provides support for a $U(1)$ Dirac QSL with singlet monopole excitations.
title Dynamical dimer structure factor of the triangular $S=1/2$ Heisenberg antiferromagnet
topic Strongly Correlated Electrons
url https://arxiv.org/abs/2604.24868