First-principles calculations of magnon-phonon and exciton-phonon interactions in 2D magnetic materials
ORAL
Abstract
Recent years have seen a growing interest in magnons – quanta of spin waves – due to their potential applications in magnon-based spintronics and quantum technologies. Therefore, the lifetime and scattering processes of magnons, which are determined by their interactions with other degrees of freedom in solids, have become interesting for both fundamental and technological reasons.
Lattice vibrations (phonons) are a major scattering channel for magnons in materials and devices. Because of their similar energies, magnons can also couple strongly with phonons, giving rise to magnon-phonon mixing (or hybridization). In this talk, I will present a unified formalism to study magnon-phonon scattering and mixing, which combines the first-principles Bethe-Salpeter equation with modern electron-phonon calculations [1,2]. This advance allow us to accurately compute magnon-phonon relaxation times and mean free paths, and identify phonon modes with strong coupling to magnons. Our study of a prototypical 2D ferromagnet, monolayer CrI3, reveals that phonons with strong magnon-phonon coupling often exhibit weak electron-phonon coupling, and vice versa. We will also show calculations of magnon-phonon mixing within the same framework, and discuss extensions to include spin-orbit coupling (SOC) and treat coupled magnons, phonons, and excitons in magnetic systems with strong SOC such as CrSBr.
Lattice vibrations (phonons) are a major scattering channel for magnons in materials and devices. Because of their similar energies, magnons can also couple strongly with phonons, giving rise to magnon-phonon mixing (or hybridization). In this talk, I will present a unified formalism to study magnon-phonon scattering and mixing, which combines the first-principles Bethe-Salpeter equation with modern electron-phonon calculations [1,2]. This advance allow us to accurately compute magnon-phonon relaxation times and mean free paths, and identify phonon modes with strong coupling to magnons. Our study of a prototypical 2D ferromagnet, monolayer CrI3, reveals that phonons with strong magnon-phonon coupling often exhibit weak electron-phonon coupling, and vice versa. We will also show calculations of magnon-phonon mixing within the same framework, and discuss extensions to include spin-orbit coupling (SOC) and treat coupled magnons, phonons, and excitons in magnetic systems with strong SOC such as CrSBr.
[1] K. B. Le, A. Esquembre-Kucukalic, H.-Y. Chen, I. Maliyov, Y. Luo, J.-J. Zhou, D. Sangalli, A. Molina-Sanchez, M. Bernardi, Phys. Rev. B (2025) (accepted). Preprint: arXiv:2502.05385v2
[2] A. E. Kucukalic, K. B. Le, A. G. Cristobal, M. Bernardi, D. Sangalli, and A. M. Sanchez, Phys. Rev. B (Accepted) Preprint: arXiv:2502.06598
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Presenters
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Khoa B Le
- Caltech