Topological charge excitations and Green's function zeros in paramagnetic Mott insulators

TL;DR

This paper explores topological charge excitations and Green's function zeros in paramagnetic Mott insulators, revealing gapless edge states and topological phase diagrams in strongly correlated systems.

Contribution

It introduces a composite operator formalism to analyze topological features in Mott insulators, highlighting the role of Green's function zeros and their relation to edge states.

Findings

Green's function zeros correspond to tightly bound holon-doublon pairs.

Both poles and zeros exhibit gapless states consistent with bulk-boundary correspondence.

Edge states include charge-carrying and charge-neutral gapless modes.

Abstract

We investigate the emergence of topological features in the charge excitations of Mott insulators in the Chern-Hubbard model. In the strong correlation regime, treating electrons as the sum of holons and doublons excitations, we compute the topological phase diagram of Mott insulators at half-filling using composite operator formalism. The Green function zeros manifest as the tightly bound pairs of such elementary excitations of the Mott insulators. Our analysis examines the winding number associated with the occupied Hubbard bands and the band of Green's function zeros. We show that both the poles and zeros show gapless states and zeros, respectively, in line with bulk-boundary correspondence. The gapless edge states emerge in a junction geometry connecting a topological Mott band insulator and a topological Mott zeros phase. These include an edge electronic state that carries a charge and a charge-neutral gapless zero mode. Our study is relevant to several twisted materials with flat bands where interactions play a dominant role.