Strain-induced nonsymmorphic symmetry breaking and removal of Dirac semimetallic nodal line in an orthoperovskite iridate

TL;DR

This study demonstrates that applying epitaxial constraints to SrIrO3 can lift its Dirac line nodes by breaking specific nonsymmorphic symmetries, transforming it from a topological semimetal to an insulator without losing key mirror symmetry.

Contribution

It reveals how epitaxial strain can selectively break nonsymmorphic symmetries to control topological states in iridate oxides, providing a pathway for engineering topological insulators.

Findings

Epitaxial constraints open a Dirac gap in SrIrO3.

Nonsymmorphic symmetry breaking is achieved without disrupting mirror symmetry.

The study links symmetry protection to n-glide operations.

Abstract

By using a combination of heteroepitaxial growth, structure refinement based on synchrotron x-ray diffraction and first-principles calculations, we show that the symmetry-protected Dirac line nodes in the topological semimetallic perovskite SrIrO3 can be lifted simply by applying epitaxial constraints. In particular, the Dirac gap opens without breaking the Pbnm mirror symmetry. In virtue of a symmetry-breaking analysis, we demonstrate that the original symmetry protection is related to the n-glide operation, which can be selectively broken by different heteroepitaxial structures. This symmetry protection renders the nodal line a nonsymmorphic Dirac semimetallic state. The results highlight the vital role of crystal symmetry in spin-orbit-coupled correlated oxides and provide a foundation for experimental realization of topological insulators in iridate-based heterostructures.