Theory of unconventional magnetism in a Cu-based kagome metal

TL;DR

This paper investigates the conditions under which unconventional magnetism can emerge in Cu-based kagome metals, combining ab initio and many-body analyses to identify magnetic order driven by electronic correlations.

Contribution

It introduces a comprehensive model framework for Cu-based kagome materials and demonstrates the emergence of unconventional magnetic order through simulations.

Findings

Unconventional magnetic order identified in Cu-based kagome metal

Correlations and Fermi surface effects crucial for magnetic fluctuations

Methodology combines ab initio and many-body analysis

Abstract

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. 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 on-site repulsion. We elucidate our methodology by analyzing the potential copper-based kagome compound CsCu$_3$Cl$_5$: From ab initio design and many-body analysis, we develop a model framework of realistic Cu-based kagome materials the simulations of which reveal unconventional magnetic order in a kagome metal.