Two-magnon response from light scattering in altermagnets
Abstract
Altermagnetism is a recently established class of magnetic order that combines fully compensated moments with momentum-dependent spin splitting, yet identifying its spectroscopic fingerprints remains an open challenge. In this work, we investigate finite-momentum two-magnon excitations in a two-dimensional d-wave altermagnet by calculating the two-magnon light scattering intensity in different polarization channels. Using linear spin-wave theory and further incorporating the leading 1/S quantum corrections, we demonstrate that the characteristic magnon splitting of altermagnets shifts the upper edge of the two-magnon continuum and the corresponding spectral features to higher energy at X=(π,0) relative to the conventional antiferromagnet, by an amount linear in the exchange anisotropy |δJ2|, while leaving the response at the Brillouin-zone center unchanged. Although magnon-magnon interactions strongly redistribute spectral weight toward lower energies, the energy scale associated with the high-energy momentum-selective reconstruction remains robust. The interactions additionally generate a pronounced low-energy two-peak structure that has no counterpart within linear spin-wave theory. At K=(π/2,π/2), we show that the interacting two-magnon resonance is twofold degenerate in the conventional antiferromagnetic phase, while a finite altermagnetic exchange anisotropy lifts this degeneracy, producing two peaks whose separation is linear in |δJ2|. The characteristic energy scales underlying both features are intrinsic to the two-magnon sector rather than to a specific scattering operator. These findings highlight the potential of finite-momentum two-magnon spectroscopy for identifying altermagnetic order in insulating magnets and motivate momentum-resolved resonant inelastic x-ray scattering studies of candidate altermagnetic materials.
Related
- Magnon Polarization Textures and Transport in Antiferromagnets and Altermagnets
- Charge-spin conversion in altermagnets: electronic anisotropy versus magnon-mediated spin drag
- A Unified Theory of Collective Magnon and Orbiton Excitations in Altermagnets
- Magnetic field effects on spin-split band and magnon transport in altermagnets and emergent compensated ferrimagnets
- Light-induced chiral altermagnets from conventional antiferromagnets
BibTeX
@misc{li2026twomagnon,
title = {{Two-magnon response from light scattering in altermagnets}},
author = {Shuyi Li and Lexu Zhao and Chunjing Jia},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09287},
eprint = {2609.09287},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09287},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Two-magnon response from light scattering in altermagnets
AU - Shuyi Li
AU - Lexu Zhao
AU - Chunjing Jia
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.09287
UR - https://arxiv.org/abs/2609.09287
AB - Altermagnetism is a recently established class of magnetic order that combines fully compensated moments with momentum-dependent spin splitting, yet identifying its spectroscopic fingerprints remains an open challenge. In this work, we investigate finite-momentum two-magnon excitations in a two-dimensional d-wave altermagnet by calculating the two-magnon light scattering intensity in different polarization channels. Using linear spin-wave theory and further incorporating the leading 1/S quantum corrections, we demonstrate that the characteristic magnon splitting of altermagnets shifts the upper edge of the two-magnon continuum and the corresponding spectral features to higher energy at X=(π,0) relative to the conventional antiferromagnet, by an amount linear in the exchange anisotropy |δJ_2|, while leaving the response at the Brillouin-zone center unchanged. Although magnon-magnon interactions strongly redistribute spectral weight toward lower energies, the energy scale associated with the high-energy momentum-selective reconstruction remains robust. The interactions additionally generate a pronounced low-energy two-peak structure that has no counterpart within linear spin-wave theory. At K=(π/2,π/2), we show that the interacting two-magnon resonance is twofold degenerate in the conventional antiferromagnetic phase, while a finite altermagnetic exchange anisotropy lifts this degeneracy, producing two peaks whose separation is linear in |δJ_2|. The characteristic energy scales underlying both features are intrinsic to the two-magnon sector rather than to a specific scattering operator. These findings highlight the potential of finite-momentum two-magnon spectroscopy for identifying altermagnetic order in insulating magnets and motivate momentum-resolved resonant inelastic x-ray scattering studies of candidate altermagnetic materials.
ER -