| Summary: | In ABO_{3} perovskites, oxygen octahedron rotations are common structural distortions that can promote large ferroelectricity in BiFeO_{3} with an R3c structure [1] but suppress ferroelectricity in CaTiO_{3} with a Pbnm symmetry [2]. For many CaTiO_{3}-like perovskites, the BiFeO_{3} structure is a metastable phase. Here, we report the stabilization of the highly polar BiFeO_{3}-like phase of CaTiO_{3} in a BaTiO_{3}/CaTiO_{3} superlattice grown on a SrTiO_{3} substrate. The stabilization is realized by a reconstruction of oxygen octahedron rotations at the interface from the pattern of nonpolar bulk CaTiO_{3} to a different pattern that is characteristic of a BiFeO_{3} phase. The reconstruction is interpreted through a combination of amplitude-contrast sub-0.1-nm high-resolution transmission electron microscopy and first-principles theories of the structure, energetics, and polarization of the superlattice and its constituents. We further predict a number of new artificial ferroelectric materials demonstrating that nonpolar perovskites can be turned into ferroelectrics via this interface mechanism. Therefore, a large number of perovskites with the CaTiO_{3} structure type, which include many magnetic representatives, are now good candidates as novel highly polar multiferroic materials [3].
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