Abstract
Theoretical analysis based on the Landau-Ginzburg-Devonshire theory is used to show that the
joint action of flexoelectric effect and rotostriction leads to a large spontaneous in-plane
polarization (1-5 lC/cm2) and pyroelectric coefficient (103 C/m2K) in the vicinity of surfaces
of otherwise non-ferroelectric ferroelastics, such as SrTiO3, with static octahedral rotations. The
origin of the improper polarization and pyroelectricity is an electric field we name flexo-roto field
whose strength is proportional to the convolution of the flexoelectric and rotostriction tensors with
octahedral tilts and their gradients. Flexo-roto field should exist at surfaces and interfaces in all
structures with static octahedral rotations, and thus, it can induce surface polar states and
pyroelectricity in a large class of otherwise nonpolar materials. VC 2012 American Institute of
Physics. [http://dx.doi.org/10.1063/1.3701152]
