Macroscopic Polarization from Antiferrodistortive Cycloids in Ferroelastic SrTiO${}_3$

Abstract

Based on a first-principles based multiscale approach, we study the polarity (P) of ferroelastic twin walls in SrTiO${}_3$. In addition to flexoelectricity, which was pointed out before, we identify two new mechanisms that crucially contribute to P: a direct "rotopolar" coupling to the gradients of the antiferrodistortive (AFD) oxygen tilts, and a trilinear coupling that is mediated by the antiferroelectric displacement of the Ti atoms. Remarkably, the rotopolar coupling presents a strong analogy to the mechanism that generates a spontaneous polarization in cycloidal magnets. We show how this similarity allows for a breakdown of macroscopic inversion symmetry (and therefore, a macroscopic polarization) in a periodic sequence of parallel twins. These results open new avenues towards engineering pyroelectricity or piezoelectricity in nominally nonpolar ferroic materials.

arXiv comment5+3 pages, 3+2 figures, 1 table

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• First principles study of ferroelastic twins in halide perovskites
• Polarity of domain boundaries in nonpolar materials derived from order parameter and layer group symmetry
• Lattice-mediated bulk flexoelectricity from first principles
• Electron trapping and detrapping in an oxide two-dimensional electron gas: The role of ferroelastic twin walls
• Bimodal Phase Diagram of the Superfluid Density in LaAlO3/SrTiO3 Revealed by an Interfacial Waveguide Resonator
• Twin Boundary Mediated Flexoelectricity in LaAlO${}_3$
• Symmetry and polarity of antiphase boundaries in PbZrO${}_3$
• Domain walls in strontium titanate
• On the possibility that PbZrO${}_3$ not be antiferroelectric