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arXiv · 2605.28698

Magnetic order, magnons, and crystal fields in van der Waals CeSiI

Wolfgang Simeth·Connor A. Occhialini·Michael E. Ziebel·Nethmi W. Hewage·Sabrina J. Li·Daniel Pajerowski·Taehun Kim·Ben Zager·Jonathan Pelliciari·Kipton Barros·Daniel Rehn·Abhay N. Pasupathy·Valentina Bisogni·Xavier Roy·Allen Scheie
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Abstract

We report neutron, X-ray absorption, and resonant X-ray spectroscopy of magnetic excitations in the new heavy-fermion van-der-Waals superconductor CeSiI. We determined effective Hamiltonians and ground states of crystal electric fields and magnons. Isotropic Heisenberg interactions on a quasi two dimensional lattice, including ferromagnetic nearest-neighbor exchange as the dominant interaction, provide an excellent account to the low-energy measured dynamics and stabilize a co-rotating spin cycloid. Our study provides the basis to model CeSiI from first principles, thereby laying the ground for microscopic understanding of heavy-fermion physics, their unconventional superconductivity, and quantum criticality.

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Wolfgang Simeth, Connor A. Occhialini, Michael E. Ziebel, Nethmi W. Hewage, Sabrina J. Li, Daniel Pajerowski, Taehun Kim, Ben Zager, Jonathan Pelliciari, Kipton Barros, Daniel Rehn, Abhay N. Pasupathy, Valentina Bisogni, Xavier Roy, Allen Scheie. 2026-05-27. Magnetic order, magnons, and crystal fields in van der Waals CeSiI. https://arxiv.org/abs/2605.28698

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