SU($N$) Quantum Spin Model with Weak and Strong First-Order Néel to Valence-Bond Solid Transitions
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arXiv
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866910141552525312 |
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| author | Flynn, Ryan Sandvik, Anders W. |
| author_facet | Flynn, Ryan Sandvik, Anders W. |
| contents | We introduce an SU($N$) symmetric two-dimensional quantum spin model, the X-Q model, which hosts a ground state transition between Néel antiferromagnetic and spontaneously dimerized states. The Q terms are products of two adjacent singlet projectors on first-neighbor sites, as in the often studied J-Q model (where J is the Heisenberg exchange), while the X terms are products of two permutation operators on second-neighbor sites. Quantum Monte Carlo simulations reveal close proximity to a deconfined quantum critical point for $N=2$, as in the J-Q model. However, for $N>2$ the transformation becomes strongly first order, contrary to conventional expectations that increasing $N$ should weaken discontinuities. We attribute this behavior to the inability of the X term, which dominates at the transition for large $N$, to induce significant U(1) fluctuations of the dimer pattern. These results provide insights into the microscopic interactions that support deconfined criticality. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_16106 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | SU($N$) Quantum Spin Model with Weak and Strong First-Order Néel to Valence-Bond Solid Transitions Flynn, Ryan Sandvik, Anders W. Strongly Correlated Electrons We introduce an SU($N$) symmetric two-dimensional quantum spin model, the X-Q model, which hosts a ground state transition between Néel antiferromagnetic and spontaneously dimerized states. The Q terms are products of two adjacent singlet projectors on first-neighbor sites, as in the often studied J-Q model (where J is the Heisenberg exchange), while the X terms are products of two permutation operators on second-neighbor sites. Quantum Monte Carlo simulations reveal close proximity to a deconfined quantum critical point for $N=2$, as in the J-Q model. However, for $N>2$ the transformation becomes strongly first order, contrary to conventional expectations that increasing $N$ should weaken discontinuities. We attribute this behavior to the inability of the X term, which dominates at the transition for large $N$, to induce significant U(1) fluctuations of the dimer pattern. These results provide insights into the microscopic interactions that support deconfined criticality. |
| title | SU($N$) Quantum Spin Model with Weak and Strong First-Order Néel to Valence-Bond Solid Transitions |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2603.16106 |