Probing the Role of A-site Cations to Charge Density Wave (CDW) Order in kagome metal AV3Sb5 (A = K, Rb, Cs) through X-ray Scattering

Abstract

The vanadium-based kagome metal, AV3Sb5 (A=K, Rb, Cs), exhibits significant effects of A-site cations on the Charge Density Wave (CDW) phase and superconductivity. Notably, (K, Cs)V3Sb5 differs from Rb counterparts, showing distinct properties, such as nematicity and various CDW domains involving 2×2×1, 2×2×2 structure. Utilizing X-ray scattering, CDW structures in AV3Sb5 (A=K, Rb, Cs) were identified. Moreover, through time-resolved X-ray scattering, we examined the influence of A-site cations on the CDW phase in CsV3Sb5 which has a relatively elevated Tc, going beyond the limitations of previous doping and pressures studies. This revealed contrasting dynamics between 2×2×1 and 2×2×2 CDW orders after the photoexcitation of conduction electrons near the Fermi surface. Especially, the 2×2×2 CDW order exhibited complex behavior involving coherent phonon linked to the A-site cation's displacement. These findings offer strong support to the hypothesis that A-site ions significantly impact the 2×2×2 CDW phase in CsV3Sb5.