Structural properties of kagome-layered crystals

Recently synthesized kagome metals AV₃Sb₅ (A=K,Rb,Cs) exhibit a Charge Density Wave (CDW) phase along with superconductivity. In this talk, we discuss the electronic and lattice properties leading to the emergence of the CDW phase in the AV3Sb5 compounds, in addition to the possibility of a similar CDW phase in other kagome-layered crystals. We extend the symmetry-based phenomenological Landau theory, originally applied to P6/mmm kagome crystals, to rhombohedrally stacked R-3m kagome systems. Finally, Density Functional Theory (DFT) is used to simulate CsV₃Sb₅ and investigate the relationship between its lattice instabilities and the van Hove singularities. We also explore M₃A₂X₂ shandites, which include rhombohedrally stacked kagome layers, using DFT and consider the effects of doping and pressure. Despite a van Hove singularity appearing at the F point in the shandites, DFT finds no signatures of a structural instability in these compounds.