Clusterization transition between cluster Mott insulators on a breathing Kagom\'{e} lattice

TL;DR

This paper investigates phase transitions between different cluster Mott insulators on a breathing Kagome lattice, revealing two types of cluster localization driven by inter-site repulsion and their relation to metallic behavior and experimental materials.

Contribution

It introduces a unified parton framework to describe multiple phases, including two cluster Mott insulators and a Fermi liquid, and analyzes their phase transitions.

Findings

Two distinct cluster Mott insulating phases identified.

Inter-site repulsion induces local metallic behavior within clusters.

Phase diagram includes transitions between insulators and a metallic phase.

Abstract

Motivated by recent experimental progress on various cluster Mott insulators, we study an extended Hubbard model on a breathing Kagom\'{e} lattice with a single electron orbital and $1/6$ electron filling. Two distinct types of cluster localization are found in the cluster Mott regime due to the presence of the electron repulsion between neighboring sites, rather than from the on-site Hubbard interaction in the conventional Mott insulators. We introduce a unified parton construction framework to accommodate both type of cluster Mott insulating phase as well as a trivial Ferm liquid metal and discuss the phase transitions in the phase diagram. It is shown that, in one of the cluster localization phases, the strong inter-site repulsion results into locally metallic behavior within one of two triangular clusters on the breathing Kagom\'{e} lattice. We further comment on experimental relevance to existing Mo-based cluster magnets.