Multimodal Topological Textures Arising from Coupled Structural Orders in SrTiO₃.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Crystallography

Background:

• Topological textures, initially observed in magnetic spin systems and polar materials, are now being explored in nonpolar structural degrees of freedom.
• Strontium titanate (SrTiO3) exhibits natural antiferrodistortive oxygen-octahedra rotations, making it a suitable prototype for studying nonpolar topologies.

Purpose of the Study:

• To investigate equilibrium domain structures and topological textures associated with antiferrodistortive oxygen-octahedra rotations in SrTiO3.
• To extend the concept of topological ordering to nonpolar structural modes.

Main Methods:

• Second-principles atomistic simulations were employed to model SrTiO3.
• Analysis of equilibrium domain structures, domain wall configurations, and vortex formation under compressive epitaxial strain.

Main Results:

• Identification of metastable 180° antiferrodistortive domain walls, distinct from common 90° walls, under compressive strain.
• Observation of complex Bloch- and Néel-like antiferrodistortive configurations, with Néel-type being energetically favored.
• Stabilization of antiferrodistortive vortex and antivortex structures co-localized with polarization vortices and modulated strain fields, forming trimodal topological textures.

Conclusions:

• The study successfully extends topological-ordering concepts to nonpolar structural modes.
• The findings open new avenues for the cross-control of distinct topological textures in materials.