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.