Correlation-driven non-trivial phases in single bi-layer Kagome intermetallics

TL;DR

This paper investigates how strong electron-electron interactions in bi-layer Kagome intermetallics can lead to exotic phases such as fractional Chern insulators and superconductivity, revealing a rich phase diagram driven by topology and correlations.

Contribution

It introduces minimal models to study the impact of strong correlations on topological bands in bi-layer Kagome systems, identifying novel phases like fractional Chern insulators and superconductors.

Findings

Topologically non-trivial bands can host fractional Chern insulator states.

Restoration of time-reversal symmetry can induce superconductivity.

Tuning nearest-neighbor repulsion causes a transition from superconducting to correlated metallic phases.

Abstract

Bi-layer Kagome compounds provide an exciting playground where the interplay of topology and strong correlations can give rise to exotic phases of matter. Motivated by recent first principles calculation on such systems (Phys. Rev. Lett 125, 026401), reporting stabilization of a Chern metal with topological nearly-flat band close to Fermi level, we build minimal models to study the effect of strong electron-electron interactions on such a Chern metal. Using approriate numerical and analytical techniques, we show that the topologically non-trivial bands present in this system at the Fermi energy can realize fractional Chern insulator states. We further show that if the time-reversal symmetry is restored due to destruction of magnetism by low dimensionality and fluctuation, the system can realize a superconducting phase in the presence of strong local repulsive interactions. Furthermore, we identify an interesting phase transition from the superconducting phase to a correlated metal by tuning nearest-neighbor repulsion. Our study uncovers a rich set of non-trivial phases realizable in this system, and contextualizes the physically meaningful regimes where such phases can be further explored.