Topological defects at octahedral tilting plethora in bi-layered perovskites

TL;DR

This paper uncovers abundant topological Z8 vortex-antivortex pairs in bi-layered perovskites, linked to oxygen octahedral tilts, revealing new insights into topological defects in these materials.

Contribution

It reports the discovery of Z8 vortex-antivortex pairs associated with oxygen octahedral tilts in bi-layered perovskites, a novel topological defect phenomenon.

Findings

Presence of Z8 vortex-antivortex pairs at phase boundary

Association of defects with oxygen octahedral tilts

Potential for new topological defect studies in perovskites

Abstract

Oxygen octahedral distortions including tilts/rotations, deformations and off-centering in (layered) perovskites play the key role in their numerous functional properties. At the polar-centrosymmetric phase boundary in bi-layered perovskite Ca3-xSrxTi2O7 with x~1, we found the presence of abundant topological Z8 vortex-antivortex pairs, associated with four oxygen octahedral tilts at domains and another four different oxygen octahedral tilts at domain boundaries. Our discovery opens a new revenue to unveil topological defects associated with various types of oxygen octahedral distortions.