TITLE: Tuning Spin-1/2 Interactions in Graphene: From Long-Range Coupling to Altermagnetic Order
AUTHOR: Beatriz Viña Bausá - Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid
WHEN: May, 28 - 12PM
WHERE: Salón de Actos, ICMM
ABSTRACT: Magnetic interactions between localized spins-½ play a central role in quantum magnetism, spin-based quantum computing, and quantum simulation. In this talk, I will show how we use scanning tunneling microscopy to manipulate individual spin-1/2 moments induced by single H atoms on graphene and quantify their exchange interactions through spin excitations [1,2]. Inelastic electron tunneling spectroscopy measurements reveal ultra-long-range ferromagnetic and antiferromagnetic coupling between H pairs governed by direct and kinetic exchange [2]. Moreover, extending these studies to three coupled spins we observe collective excitations and coupling asymmetries arising from graphene’s valley–Kekulé degrees of freedom. Building on these results, we show how spin-group symmetry rules enable a bottom-up route toward unconventional magnetic phases in hydrogenated graphene, including altermagnetism [3]. These findings are supported by mean-field Hubbard and density functional theory calculations.
Our work establishes hydrogenated graphene as a powerful platform for simulating exotic spin models and exploring symmetry-driven magnetism in two dimensions.
References:
[1] H. González-Herrero et al., Science 352 (2016) 437.
[2] B. Viña-Bausá et al., Nat. Commun (2026) (arXiv:2511.06887).
[3] B. Viña-Bausá et al., Nano Lett. 25 (2025) 11554-11561.
