Electron-Correlation-Induced Charge Density Wave in FeGe

As the first magnetic kagome material to exhibit the charge density wave（CDW） order,FeGe has attracted much attention in recent research.Similar to AV3Sb5（A=K,Cs,Rb）,FeGe exhibits the CDW pattern with an in-plane 2×2 structure and the existence of van Hove singularities near the Fermi level.However,sharply different from AV3Sb5 which has phonon instability at M point,all the theoretically calculated phonon frequencies in FeGe remain positive.Based on first-principles calculations,we surprisingly find that the maximum of nesting function is at K point instead of M point.Two Fermi pockets with Fe-dxz and Fe-dx2-y2/dxy orbital characters have large contribution to the Fermi nesting,which evolve significantly with kz,indicating the highly three-dimensional（3D）feature of FeGe in contrast to AV3Sb5.Considering the effect of local Coulomb interaction,we reveal that the instability at K point is significantly suppressed due to the sublattice interference mechanism.Meanwhile,the wave functions nested by vector M have many ingredients located at the same Fe site,thus the instability at M point is enhanced.This indicates that the electron correlation,rather than electron-phonon interaction,plays a key role in the CDW transition at M point.