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arXiv · 1803.11082

Macroscopic Polarization from Antiferrodistortive Cycloids in Ferroelastic SrTiO$_3$

Andrea Schiaffino·Massimiliano Stengel
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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.

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Andrea Schiaffino, Massimiliano Stengel. 2018-03-29. Macroscopic Polarization from Antiferrodistortive Cycloids in Ferroelastic SrTiO$_3$. https://doi.org/10.1103/physrevlett.119.137601

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