X. Z. Lu, X. G. Gong, H. J. Xiang
Interface engineering in perovskite oxide superlattices has developed into a flourishing field, enabling not only further tuning of the exceptional properties, but also giving access to emergent physical phenomena. Here, we reveal a new mechanism for enhancing the electric polarization by the interfacial oxygen octahedral tilts in BaTiO3/CaTiO3 superlattices. By combining a novel genetic algorithm with density functional theory (DFT), we predict that the true ground states in 1:1 and 2:2 BaTiO3/CaTiO3 superlattices grown on SrTiO3 adopt the Pc symmetry with a large electric polarization (32.7{\mu}C/cm2 for 1:1 and 34.0 {\mu}C/cm2 for 2:2 superlattices), which is even larger than that of bulk BaTiO3. The tilt of oxygen octahedron is found to play a key role for the enhancement of out-of-plane polarization because it reduces greatly the rotation of oxygen octahedron which significantly suppresses the out-of-plane polarization.
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http://arxiv.org/abs/1308.0076
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