Sunday, August 4, 2013

1308.0076 (X. Z. Lu et al.)

Polarization Enhancement in Perovskite Superlattices by Oxygen
Octahedral Tilts

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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