Interaction-resistant metals in multicomponent Fermi systems

TL;DR

This paper demonstrates that interaction-resistant metallic states can emerge in multicomponent Fermi systems, including multiorbital Hubbard models with Hund's coupling and SU(3) models with patterned potentials, as a compromise between competing insulating phases.

Contribution

It provides analytical and numerical evidence that Hund's metals are a specific case of a broader phenomenon of interaction-resistant metals in strongly correlated systems.

Findings

Interaction-resistant metals arise as a compromise between different insulating solutions.

Both models exhibit a metallic ground state despite large Coulomb repulsion.

The phenomenon is general and can be realized in various strongly correlated systems.

Abstract

We analyze two different fermionic systems that defy Mott localization showing a metallic ground state at integer filling and very large Coulomb repulsion. The first is a multiorbital Hubbard model with a Hund's coupling, where this physics has been widely studied and the new metallic state is called a Hund's metal, and the second is a SU(3) Hubbard model with a patterned single-particle potential designed to display a similar interaction-resistant metal in a set-up which can be implemented with SU($N$) ultracold atoms. With simple analytical arguments and exact numerical diagonalization of the Hamiltonians for a minimal three-site system, we demonstrate that the interaction-resistant metal emerges in both cases as a compromise between two different insulating solutions which are stabilized by different terms of the models. This provides a strong evidence that the Hund's metal is a specific realization of a more general phenomenon which can be realized in various strongly correlated systems.