Reevaluating quantum geometric criteria for itinerant magnetic instabilities
Phys. Rev. B 114, 204402 – Published 1 October, 2026
DOI: https://doi.org/10.1103/83rk-rkcf
Abstract
The interplay between quantum geometry and electron correlation has emerged as a compelling paradigm in quantum many-body physics. Recent studies have highlighted the diagnostic utility of quantum geometry in identifying magnetic instabilities within itinerant electron systems. In the present work, we critically reexamine these theoretical proposals, which are commonly formulated within the random phase approximation (RPA). To this end, we reformulate the matrix-based RPA instability criterion in the channel representation for generic two-orbital systems, explicitly accounting for multiple channels of magnetic ordering. Our results demonstrate that magnetic phase transitions are intricately governed by the interplay between the bare susceptibility tensor and the spin interaction matrix. Consequently, prior assertions that instabilities can be predicted solely from the quantum geometric structure of a single-channel susceptibility are valid only under complete channel decoupling in both the interaction and susceptibility matrices. By adopting the channel representation, our formulation achieves greater physical transparency and computational tractability compared to the conventional orbital-space approach, thereby furnishing a promising alternative for advancing theoretical studies of complex multiorbital systems.
