Strain-dependent charge density wave stability in monolayer Kagome AV3Sb5 (A = K, Rb, Cs)

We perform first-principles calculations based on density-functional theory to study the stability of a charge density wave (CDW) phase in Kagome metals AV 3 Sb 5 (A = K, Rb, Cs) in the monolayer form. The energy gain of the CDW formation from the pristine structure increases from A = K to Cs with increasing lattice parameter. We find that the CDW phase is further stabilized by expanding the lattice for A = K while it is most stable around the equilibrium value in case of A = Cs, suggesting the lattice parameter as a main factor of differentiating the relative stability of the CDW phase among alkali elements for A. It is revealed that the maximum CDW stability is associated with the Fermi energy located in between two van Hove singularities each at Γ and M k-points, providing a comprehensive understanding of the CDW formation and its stability as a function of the strain as well as the alkali element in these materials. • First-principles study on the monolayer Kagome materials AV 3 Sb 5 (A=K, Rb, and Cs) • Strain and alkali atom dependence on the charge-density-wave stability • Maximum stability with the Fermi level in the middle of van-Hove points • Providing a unified view on the mechanism of the charge-density-wave formation