Theory of unconventional magnetism in a Cu-based kagome metal

Kagome metals have established a new arena for correlated electron physics. To date, the predominant experimental evidence centers around unconventional charge order, nematicity, and superconductivity, while magnetic fluctuations due to electronic interactions, i.e., beyond local atomic magnetism, have largely been elusive. From ab initio design and many-body analysis, we develop a model framework of Cu-based kagome materials the simulations of which reveal unconventional magnetic order in a kagome metal. We find the challenge of locating the appropriate parameter regime for such exotic order to center around two aspects. First, the correlations implied by low-energy orbitals have to be sufficiently large to yield a dominance of magnetic fluctuations and weak to retain an itinerant parent state. Second, the kinematic kagome profile at the Fermi level demands an efficient mitigation of sublattice interference causing the suppression of magnetic fluctuations descending from electronic onsite repulsion. We elucidate our methodology by analyzing the proposed compound CsCu$_3$Cl$_5$, assessing its feasibility for future material synthesis.