Electron correlations in the kagome flat band metal CsCr₃Sb₅

Kagome metals offer a unique platform for investigating robust electron-correlation effects because of their lattice geometry, flat bands and multi-orbital nature. In the cases with active flat bands, recent theoretical studies have pointed to a rich phase diagram that contains not only electronic orders but also quantum criticality. CsCr₃Sb₅ has emerged as a strong candidate for exploring such new physics. Here, using effective tight-binding models obtained from ab initio calculations, we study the effects of electronic correlations and symmetries on the electronic structure of CsCr₃ Sb₅. The effective tight-binding model and Fermi surface comprise multiple Cr-d orbitals and Sb-p orbitals. The introduction of Hubbard-Kanamori interactions leads to orbital-selective band renormalization dominated by the dₗₙ band, concurrently producing emergent flat bands very close to the Fermi level. Our analysis sets the stage for further investigations into the electronic properties of CsCr₃Sb₅, including electronic orders, quantum criticality and unconventional superconductivity, which promise to shed much new light into the electronic materials with frustrated lattices and bring about new connections with the correlation physics of a variety of strongly correlated systems.