We present a combined computational and experimental study of Nb3Cl8, a correlated layered material containing Nb trimers, through the lens of competing intra- and intercluster interactions. Different proposed explanations for its magnetostructural transition such as charge disproportionation, antiferromagnetic quenching, and interlayer singlet formation are investigated in light of the various reported low-temperature structures. Our findings rule out the previously proposed charge-disproportionation, suggest an intricate interplay between Mott physics and the formation of interlayer singlets, and also hint at a possible explanation of the observed intratrimer scissoring distortion. We suggest that the physics of Nb3Cl8 should be understood in the context of weakly coupled Hubbard dimers.
@article{arxiv.2509.03988,
title = {Hubbard dimer physics and the magnetostructural transition in the correlated cluster material Nb$_3$Cl$_8$},
author = {Alberto Carta and Peter Mlkvik and Fabian Grahlow and Markus Ströbele and H. -Jürgen Meyer and Carl P. Romao and Nicola A. Spaldin and Claude Ederer},
journal= {arXiv preprint arXiv:2509.03988},
year = {2025}
}