Cr-Substitution-Driven Correlation Enhancement and Hund's Metallicity in CsV_3-xCr_xSb₅

The Kagome metal CsV₃Sb₅ transitions from a weakly correlated state to a strongly correlated one upon Cr substitution, yet the mechanism driving this enhancement remains an open question. Here, we employ a combination of density functional theory and dynamical mean-field theory (DFT+DMFT) to systematically investigate the evolution of electronic correlations in the CsV_3-xCr_xSb₅ (x = 0, 1, and 3) series. Our calculations reveal that Cr doping drives the system into a strongly correlated Hund’s metal phase, characterized by significant and orbital-dependent enhancements in quasiparticle effective masses and electronic scattering rates. We trace the origin of this transition to a doping-induced shift from low-spin to high-spin atomic configurations. This preference for high-spin states, which is promoted by the near half-filling of the Cr d-orbitals, induces a pronounced orbital blocking effect that strengthens correlations. Our findings establish that Hund’s coupling is the decisive factor governing the rich correlation physics in the CsV_3-xCr_xSb₅ family, providing a tunable platform for exploring Hund's metallicity.