Ab initio study of $Z_2$ topological phases in perovskite (111) $(\text{SrTiO}_3)_7/(\text{SrIrO}_3)_2$ and $(\text{KTaO}_3)_7/(\text{KPtO}_3)_2$ multilayers

TL;DR

This study combines tight binding and ab initio methods to explore topological phases in perovskite multilayers, revealing a topological semimetal and a tunable topological Mott insulator.

Contribution

It provides a detailed analysis of topological phases in specific perovskite multilayers using ab initio calculations and models, highlighting their potential for phase control.

Findings

$( ext{SrTiO}_3)_7/( ext{SrIrO}_3)_2$ is a topological semimetal

$( ext{KTaO}_3)_7/( ext{KPtO}_3)_2$ is a topological Mott insulator

External electric field can induce a phase transition in the latter

Abstract

Honeycomb structures formed by the growth of perovskite 5d transition metal oxide heteroestructures along the (111) direction in $t_{2g}^5$ configuration can give rise to topological ground states characterized by a topological index $\nu$=1. Using a combination of a tight binding model and ab initio calculations we study the multilayers $(\text{SrTiO}_3)_7/(\text{SrIrO}_3)_2$ and $(\text{KTaO}_3)_7/(\text{KPtO}_3)_2$ as a function of parity asymmetry, on-site interaction and uniaxial strain and determine the nature and evolution of the gap. $(\text{SrTiO}_3)_7/(\text{SrIrO}_3)_2$ is found to be a topological semimetal. $(\text{KTaO}_3)_7/(\text{KPtO}_3)_2$ is a topological Mott insulator that can be driven to a trivial insulating phase by an external electric field.