Charge density waves and electronic properties of superconducting kagome metals

Kagome metals AV3Sb5 (A=K, Rb, and Cs) exhibit intriguing superconductivity below 0.9∼2.5  K, a charge density wave (CDW) transition around 80∼100  K, and Z2 topological surface states. We investigate the electronic and structural properties of CDW by first-principles calculations. We reveal an inverse Star of David deformation as the 2×2 CDW ground state of the kagome lattice. The kagome lattice shows softening breathing-phonon modes, indicating the structural instability. We investigate roles of Fermi surface nesting for the CDW transition via the electronic susceptibility. We further analyze impacts of hole doping to CDW and compare our results with recent experiments.