Valence-bond-solid domain walls in a 2D quantum magnet

Akimasa Miyake

Munehisa Matsumoto

Adam Iaizzi, Anders W. Sandvik

Hui Shao, Wenan Guo, Anders W. Sandvik

We present a projector quantum Monte Carlo study of the topological properties of the valence-bond-solid ground state in the J-Q 3 spin model on the square lattice. The winding number is a topological number counting the number of domain walls in the system and is a good quantum number in the thermodynamic limit. We study the finite-size behavior and obtain the domain wall energy density for a topological nontrivial valence-bond-solid state.

Indrani Bose

Zhi-Yao Ning, Xue-Feng Zhang, Naoki Kawashima +1 more

Quantum magnets provide a microscopic platform for studying confinement and gauge-constrained structures mediated by emergent gauge fields. We investigate confined spinon complexes in the columnar valence-bond-solid (VBS) phase near deconfined quantum criticality using pinned-spin defects and quantum Monte Carlo simulations. The pinned spins act as static spinon sources with controlled positions, spin projections, and VBS vorticities, enabling measurement of defect energies and direct real-space visualization of the associated VBS domain-wall strings. For matched spinon-antispinon sources, the excitation energy saturates beyond a characteristic separation as one extended dipole reorganizes into two shorter neutral dipoles, providing energetic and real-space evidence of string breaking. We further show that domain-wall connectivity is governed by lattice-scale VBS phase offsets in addition to vorticity and spin-projection neutrality. Compatible multi-pin patterns generate connected four-spinon complexes and extended domain-wall networks that retain their global connectivity under local distortions. These results establish pinned-spin defects as a controlled tool for assembling and resolving multi-spinon structures and their confining strings in a VBS phase.