Among the family of intercalated transition-metal dichalcogenides (TMDs), FexNbS2 is found to possess unique current-induced resistive switching behaviors, tunable antiferromagnetic states, and a commensurate charge order, all of which are tied to a critical Fe doping of xc = 1/3. However, the electronic origin of such extreme stoichiometry sensitivities remains unclear. Combining angle-resolved photoemission spectroscopy (ARPES) with density functional theory (DFT) calculations, we identify and characterize a dramatic eV-scale electronic restructuring that occurs across the xc. Moment-carrying Fe 3dz2 electrons manifest as narrow bands within 200 meV of the Fermi level, distinct from other transition metal intercalated TMD magnets. These states strongly hybridize with itinerant electrons in TMD layer, rapidly lose coherence above xc due to correlation-driven effects. This sudden quasiparticle decoherence collapses the Fe-Nb hybridization, which explicitly suppresses the out-of-plane effective Fe-Fe exchange interaction, driving the transformation of the magnetic ground state from an antiferromagnetic stripe phase to a zigzag phase. These observations resemble the exceptional electronic and magnetic sensitivity of strongly correlated systems, and demonstrate that quantifying orbital-specific hybridization via ARPES offers an alternative pathway to evaluate effective magnetic exchange in metallic magnets, complementing inelastic neutron and resonant x-ray scattering probes.
@article{arxiv.2509.03327,
title = {Electronic origin of delicate antiferromagnetism in Fe$_{x}$NbS$_2$},
author = {Wenxin Li and Jonathan T. Reichanadter and Shan Wu and Ji Seop Oh and Rourav Basak and Shannon C. Haley and Siqi Wang and Joshua E. Chaparro Mata and Elio Vescovo and Donghui Lu and Makoto Hashimoto and Christoph Klewe and Suchismita Sarker and Jessica L. McChesney and Alex Frañó and James G. Analytis and Robert J. Birgeneau and Jeffrey B. Neaton and Yu He},
journal= {arXiv preprint arXiv:2509.03327},
year = {2026}
}