Higher-Order Topological Mott Insulator on the Pyrochlore Lattice

TL;DR

This paper provides the first unbiased numerical evidence for a higher-order topological Mott insulator in three dimensions, revealing a novel phase with corner-localized spin excitations connected to a third-order topological insulator.

Contribution

It demonstrates the existence of a higher-order topological Mott insulator in 3D using quantum Monte Carlo simulations, linking it to a noninteracting third-order topological insulator.

Findings

Identification of a 3D higher-order topological Mott insulator

Connection to a noninteracting third-order topological insulator

Observation of a topological phase transition via bulk spin gap closure

Abstract

We provide the first unbiased evidence for a higher-order topological Mott insulator in three dimensions by numerically exact quantum Monte Carlo simulations. This insulating phase is adiabatically connected to a third-order topological insulator in the noninteracting limit, which features gapless modes around the corners of the pyrochlore lattice and is characterized by a $\mathbb{Z}_{4}$ spin-Berry phase. The difference between the correlated and non-correlated topological phases is that in the former phase the gapless corner modes emerge only in spin excitations being Mott-like. We also show that the topological phase transition from the third-order topological Mott insulator to the usual Mott insulator occurs when the bulk spin gap solely closes.