Coupled topological flat and wide bands: Quasiparticle formation and destruction

Flat bands amplify correlation effects and are of extensive current interest. They provide a platform to explore both topology in correlated settings and correlation physics enriched by topology. Recent experiments in correlated kagome metals have found evidence for strange-metal behavior. A major theoretical challenge is to study the effect of local Coulomb repulsion when the band topology obstructs a real-space description. In a variant to the kagome lattice, we identify an orbital-selective Mott transition in any system of coupled topological flat and wide bands. This was made possible by the construction of exponentially localized and Kramers-doublet Wannier functions, which, in turn, leads to an effective Kondo-lattice description. Our findings show how quasiparticles are formed in such coupled topological flat-wide band systems and, equally important, how they are destroyed. Our work provides a conceptual framework for the understanding of the existing and emerging strange-metal properties in kagome metals and beyond.

Automated summary

Flat bands enhance correlation effects and have gained significant attention. They offer a platform to explore topology in correlated systems and correlation physics enriched by topology. Recent experiments in correlated kagome metals have observed strange-metal behavior. The challenge lies in studying the impact of local Coulomb repulsion when band topology hinders a real-space description. In a modified kagome lattice, we have discovered an orbital-selective Mott transition in any system with coupled topological flat and wide bands. This is made possible through the use of exponentially localized and Kramers-doublet Wannier functions, leading to an effective Kondo-lattice description. Our findings shed light on the formation and destruction of quasiparticles in such coupled topological flat-wide band systems, providing a conceptual framework to understand the strange-metal properties in kagome metals and beyond.