Ultra-long-range spin coupling in graphene revealed by atomically resolved spin excitations.

Viña-Bausá, Beatriz; Costa, António Tavares; Henriques, Joao; Cortés-Del Río, Eva; Carrasco, Roberto; Mallet, Pierre; Veuillen, Jean-Yves; Fernández-Rossier, Joaquín et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

Magnetic interactions between localized spins-½ play a central role in quantum magnetism, spin-based quantum computing, and quantum simulation. The range and strength of these interactions are key figures of merit. Here, we probe exchange interactions in pairs of spins-½ introduced by chemisorption of individual hydrogen atoms on graphene. Using scanning tunneling microscopy and inelastic electron tunneling spectroscopy, supported by large-scale mean-field Hubbard calculations, we demonstrate 3 meV exchange couplings at separations beyond 10 nm, surpassing all prior systems. The couplings can be ferro- or antiferromagnetic depending on the relative sublattice arrangement. Real-space mapping of spin excitation amplitudes enables characterization with atomic-resolution. Through atomic manipulation we extend this control to spin trimers, revealing collective spin excitations when pairwise exchange couplings are comparable.