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arXiv · 2412.20743

Magnetic excitations and interactions in the Weyl ferrimagnet NdAlSi

Chris J. Lygouras·Hung-Yu Yang·Xiaohan Yao·Jonathan Gaudet·Yiqing Hao·Huibo Cao·Jose A. Rodriguez-Rivera·Andrey Podlesnyak·Stefan Blügel·Predrag Nikolić·Fazel Tafti·Collin L. Broholm
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Abstract

Weyl fermions can arise from time-reversal symmetry-breaking magnetism, but their impact on magnetic order is a source of ongoing research. Using high-precision neutron diffraction and spectroscopy, we present a comprehensive exploration of the magnetic structure and excitation spectrum of Weyl semimetal and helical magnet NdAlSi. We use Luttinger-Tisza, classical mean-field, and random-phase approximation techniques to model the dispersive crystal field excitons. We find extended-ranged and sign-changing interactions, suggesting a coupling between conduction electrons and the local moments. We demonstrate that low-symmetry anisotropic Dzyaloshinskii-Moriya interactions, in contrast with higher-symmetry interactions enabled by Weyl fermions, play an important role in stabilizing the complex spin spiral ground state of NdAlSi. Our work provides a first detailed view of microscopic interactions in a Weyl magnet, and constrains the role of Weyl electrons and their chirality on the spiral magnetism.

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Chris J. Lygouras, Hung-Yu Yang, Xiaohan Yao, Jonathan Gaudet, Yiqing Hao, Huibo Cao, Jose A. Rodriguez-Rivera, Andrey Podlesnyak, Stefan Blügel, Predrag Nikolić, Fazel Tafti, Collin L. Broholm. 2024-12-30. Magnetic excitations and interactions in the Weyl ferrimagnet NdAlSi. https://arxiv.org/abs/2412.20743

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