Disordered flat bands on the kagome lattice

TL;DR

This paper investigates disordered flat bands on the kagome lattice, providing exact solutions and exploring their topological and magnetic properties, including ferromagnetism in disordered systems.

Contribution

It introduces two models with correlated disorder on the kagome lattice, revealing exact flat band solutions and analyzing their topological and magnetic characteristics.

Findings

Exact flat band solutions in disordered kagome models

Band touching not protected by topology

Disordered flat band ferromagnetism observed

Abstract

We study two models of correlated bond- and site-disorder on the kagome lattice considering both translationally invariant and completely disordered systems. The models are shown to exhibit a perfectly flat ground state band in the presence of disorder for which we provide exact analytic solutions. Whereas in one model the flat band remains gapped and touches the dispersive band, the other model has a finite gap, demonstrating that the band touching is not protected by topology alone. Our model also displays fully saturated ferromagnetic groundstates in the presence of repulsive interactions, an example of disordered flat band ferromagnetism.