# Higher-order Topological Mott Insulators

## TL;DR

This paper introduces a novel correlated topological phase called higher-order topological Mott insulator (HOTMI), characterized by bulk-boundary correspondence with gapless corner spin excitations, demonstrated in a kagome lattice Hubbard model.

## Contribution

It proposes the HOTMI state, revealing how strong correlations induce unique corner modes in a topological Mott insulator, expanding understanding of correlated topological phases.

## Key findings

- HOTMI exhibits gapless corner spin modes due to electron correlations.
- Bulk properties are characterized by Z3 spin-Berry phase.
- Strong correlations modify corner modes from the noninteracting case.

## Abstract

We propose a new correlated topological state which we call a higher-order topological Mott insulator (HOTMI). This state exhibits a striking bulk-boundary correspondence due to electron correlations. Namely, the topological properties in the bulk, characterized by the Z3 spin-Berry phase, result in gapless corner modes emerging only in spin excitations (i.e., the single-particle excitations remain gapped around the corner). We demonstrate the emergence of the HOTMI in a Hubbard model on the kagome lattice, and elucidate how strong correlations change gapless corner modes at the noninteracting case.