Magnetic excitations of the strongly-anisotropic triangular XXZ model: a projected spin-product state approach
Abstract
Recent experiments have sparked interest on the ground-state properties and on the excitation spectrum of the spin-1/2 triangular XXZ model with strong Ising-like anisotropy. In this work, we introduce and analyze a ``projected'' coherent-state approximation to the model, constructed by projecting spin-product states onto the low-energy configurations of the triangular Ising antiferromagnet. Within this approximation, we discuss the structure of the ground-state ordering and the magnetization curve under a longitudinal field. We then discuss the excitation spectrum by linearizing equations of motion deriving from a time-dependent variational principle. This leads to a natural description of spin-wave-like excitations within the strongly constrained Hilbert space. At zero field, the variational approximation leads to a very flat landscape of quasi-degenerate states, which results in a low-energy pseudo-Goldstone mode in the excitation spectrum. We compare our results to experimental measurements on the cobaltite K2Co(SeO3)2 (KCSO). Our approximation leads to a dramatic improvement as compared to linear spin-wave theory. However, there remain deviations in the value of the pseudo-Goldstone gap and in the dispersion near M points at low field.
Related
- Emergence of nonequilibrium Lieb excitations in periodically-driven strongly-interacting bosons
- Anisotropic magneto-elastic coupling in the quasi-2D Ising magnet Li2FeSiO4 and thermodynamic signature of low-energy orbital excitations
- Collective charge excitations in the kagome lattice driven by Holstein phonons and magnetic fields
- Thermal quasi-Devil's staircase in an anisotropic triangular-lattice Rydberg array
- Multiorbital Anisotropy and Magnetic Excitations in Trilayer Nickelate Pr4Ni3O10
BibTeX
@misc{mauri2026magnetic,
title = {{Magnetic excitations of the strongly-anisotropic triangular XXZ model: a projected spin-product state approach}},
author = {Achille Mauri and Frédéric Mila},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.36140},
eprint = {2609.36140},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36140},
}
RIS
TY - UNPB
TI - Magnetic excitations of the strongly-anisotropic triangular XXZ model: a projected spin-product state approach
AU - Achille Mauri
AU - Frédéric Mila
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.36140
UR - https://arxiv.org/abs/2609.36140
AB - Recent experiments have sparked interest on the ground-state properties and on the excitation spectrum of the spin-1/2 triangular XXZ model with strong Ising-like anisotropy. In this work, we introduce and analyze a ``projected'' coherent-state approximation to the model, constructed by projecting spin-product states onto the low-energy configurations of the triangular Ising antiferromagnet. Within this approximation, we discuss the structure of the ground-state ordering and the magnetization curve under a longitudinal field. We then discuss the excitation spectrum by linearizing equations of motion deriving from a time-dependent variational principle. This leads to a natural description of spin-wave-like excitations within the strongly constrained Hilbert space. At zero field, the variational approximation leads to a very flat landscape of quasi-degenerate states, which results in a low-energy pseudo-Goldstone mode in the excitation spectrum. We compare our results to experimental measurements on the cobaltite K_2Co(SeO_3)_2 (KCSO). Our approximation leads to a dramatic improvement as compared to linear spin-wave theory. However, there remain deviations in the value of the pseudo-Goldstone gap and in the dispersion near M points at low field.
ER -