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 A V 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 A V 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. Analysis of the antiferromagnetic ordered phase of kagome lattice FeGe suggests that charge density wave is the result of a combination of electronic-correlations-driven antiferromagnetic order and instability driven by van Hove singularities.