Quantum skyrmion molecule: two quantum skyrmions bound by coherent magnon exchange
Abstract
Quantum skyrmions in frustrated spin-1/2 magnets are bound states of a few flipped spins in a ferromagnetic background. Using exact diagonalization and density-matrix renormalization group calculations for the J1--J2 triangular-lattice model with easy-axis anisotropy K, we ask what happens when two such objects are brought together. The binding energy per flipped spin of a single skyrmion has a minimum at Nf*=7 for K=0.02--$0.04$, and skyrmions smaller than Nf* do not exist as pairs: at any distance they coalesce into a single larger object, and pinning wells cannot prevent it. Two skyrmions of natural size, by contrast, form a bound molecule without pinning or external field, with binding energy U≃−0.007J1 at K=0.03--$0.04$ and an equilibrium separation of $5.5$ lattice spacings that does not depend on K or on the size of the simulation domain; at K=0.02, where the single skyrmion is itself marginally bound, the pair is unbound within our resolution. The two constituents keep their identity (7+7 flipped spins) and are coupled by a coherent exchange of magnons, visible as number fluctuations between the two halves of the domain in excess of those of two independent skyrmions and as in-plane spin correlations between the two skyrmion walls that reach $0.16$ across the gap. These correlations follow the vortex pattern of the two textures and lock their relative helicity, the quantum counterpart of the helicity-dependent interaction of classical skyrmions. We discuss the molecule as a self-assembled two-qubit element for skyrmion helicity qubits in a single layer.
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BibTeX
@misc{silva2026quantum,
title = {{Quantum skyrmion molecule: two quantum skyrmions bound by coherent magnon exchange}},
author = {Ricardo L. Silva},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.17299},
eprint = {2610.17299},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.17299},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Quantum skyrmion molecule: two quantum skyrmions bound by coherent magnon exchange
AU - Ricardo L. Silva
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2610.17299
UR - https://arxiv.org/abs/2610.17299
AB - Quantum skyrmions in frustrated spin-1/2 magnets are bound states of a few flipped spins in a ferromagnetic background. Using exact diagonalization and density-matrix renormalization group calculations for the J_1--J_2 triangular-lattice model with easy-axis anisotropy K, we ask what happens when two such objects are brought together. The binding energy per flipped spin of a single skyrmion has a minimum at Nf^*=7 for K=0.02--$0.04$, and skyrmions smaller than Nf^* do not exist as pairs: at any distance they coalesce into a single larger object, and pinning wells cannot prevent it. Two skyrmions of natural size, by contrast, form a bound molecule without pinning or external field, with binding energy U≃−0.007J_1 at K=0.03--$0.04$ and an equilibrium separation of $5.5$ lattice spacings that does not depend on K or on the size of the simulation domain; at K=0.02, where the single skyrmion is itself marginally bound, the pair is unbound within our resolution. The two constituents keep their identity (7+7 flipped spins) and are coupled by a coherent exchange of magnons, visible as number fluctuations between the two halves of the domain in excess of those of two independent skyrmions and as in-plane spin correlations between the two skyrmion walls that reach $0.16$ across the gap. These correlations follow the vortex pattern of the two textures and lock their relative helicity, the quantum counterpart of the helicity-dependent interaction of classical skyrmions. We discuss the molecule as a self-assembled two-qubit element for skyrmion helicity qubits in a single layer.
ER -