Discovery of charge density wave in a kagome lattice antiferromagnet

A hallmark of strongly correlated quantum materials is the rich phase diagram resulting from competing and intertwined phases with nearly degenerate ground-state energies(1,2). A well-known example is the copper oxides, in which a charge density wave (CDW) is ordered well above and strongly coupled to the magnetic order to form spin-charge-separated stripes that compete with superconductivity(1,2). Recently, such rich phase diagrams have also been shown in correlated topological materials. In 2D kagome lattice metals consisting of corner-sharing triangles, the geometry of the lattice can produce flat bands with localized electrons(3,4), non-trivial topology(5-7), chiral magnetic order(8,9), superconductivity and CDW order(10-15). Although CDW has been found in weakly electron-correlated non-magnetic AV(3)Sb(5) (A = K, Rb, Cs)(10-15), it has not yet been observed in correlated magnetic-ordered kagome lattice metals(4,16-21). Here we report the discovery of CDW in the antiferromagnetic (AFM) ordered phase of kagome lattice FeGe (refs. (16-19)). The CDW in FeGe occurs at wavevectors identical to that of AV(3)Sb(5) (refs. (10-15)), enhances the AFM ordered moment and induces an emergent anomalous Hall effect(22,23). Our findings suggest that CDW in FeGe arises from the combination of electron-correlations-driven AFM order and van Hove singularities (vHSs)-driven instability possibly associated with a chiral flux phase(24-28), in stark contrast to strongly correlated copper oxides(1,2) and nickelates(29-31), in which the CDW precedes or accompanies the magnetic order.

Automated summary

A hallmark of strongly correlated quantum materials is the rich phase diagram resulting from competing and intertwined phases. Recently, such rich phase diagrams have also been shown in correlated topological materials. This study reports the discovery of CDW in the antiferromagnetic ordered phase of kagome lattice FeGe, which is caused by the combination of electron-correlated AFM order and van Hove singularities-driven instability.