First principles theory of charge density wave state and magnetism in kagome metals AV₃Sb₅

The recently discovered Kagome metals AV₃Sb₅ (A = Cs, Rb or K) have attracted great attention due to the coexistence of nontrivial band topology and strong correlations, which produce versatile physics such as charge-density wave (CDW), magnetism, and superconductivity. However, the formation mechanisms of the various correlated states are still under debate. Here we theoretically study the Fermi-surface instabilities of AV₃Sb₅ based on first principles calculations, both for the normal phase and the 22 CDW phase. In particular, we have calculated generalized susceptibilities defined in the charge-orbital-spin space within random phase approximation based on Wannierized tight-binding models, and find that there is no instability mode at M point driven by electron-electron interactions. Instead, we find magnetic instabilities at Γ point, which are further confirmed by unrestricted self-consistent Hartree-Fock calculations including both on-site and inter-site Coulomb interactions. Our results suggest the CDW phase is more likely to be driven by electron-phonon couplings, while electron-electron Coulomb interactions may give rise to magnetism which may contribute to anomalous Hall effect.