Stabilizing hidden room-temperature ferroelectricity via a metastable atomic distortion pattern

Abstract

Nonequilibrium atomic structures can host exotic and technologically relevant properties in otherwise conventional materials. Oxygen octahedral rotation forms a fundamental atomic distortion in perovskite oxides, but only a few patterns are predominantly present at equilibrium. This has restricted the range of possible properties and functions of perovskite oxides, necessitating the utilization of nonequilibrium patterns of octahedral rotation. Here, we report that a designed metastable pattern of octahedral rotation leads to robust room-temperature ferroelectricity in CaTiO3, which is otherwise nonpolar down to 0 K. Guided by density-functional theory, we selectively stabilize the metastable pattern, distinct from the equilibrium pattern and cooperative with ferroelectricity, in heteroepitaxial films of CaTiO3. Atomic-scale imaging combined with deep neural network analysis confirms a close correlation between the metastable pattern and ferroelectricity. This work reveals a hidden but functional pattern of oxygen octahedral rotation and opens avenues for designing multifunctional materials.

Asymmetric interfaces and high-TC ferromagnetic phase in La0.67Ca0.33MnO3/SrRuO3 superlattices

“…Combining DFT-calculated interfacial charge redistribution and STEM results, we confirm that the opposite polar distortions could be driven by an ionic screening of the uncompensated charges at the MnO2-SrO-and (La,Ca)O-RuO2-terminated interfaces. In perovskite-structured oxides, such a polar distortion commonly competes with and suppresses the octahedral rotation [25,49,69,70]. This trend is also suggested by the DFT simulation shown in Fig.…”

Structural Phase Transition and In-Situ Energy Storage Pathway in Nonpolar Materials: A Review

“…This broadens the perspectives of understanding the origins of ferroelectricity and implies that more nonpolar dielectrics with typical AFD order [92,93] can be transformed to novel FD phases under excitation of an external field [97]. Being compatible with chemical, defect and strain engineering [30,98], therefore, the range of candidate energy storage systems can be greatly expanded by the AFD-to-FD transition.…”

“…This broadens the perspectives of understanding the origins of ferroelectricity and implies that more nonpolar dielectrics with typical AFD order [92,93] can be transformed to novel FD phases under excitation of an external field [97]. Being compatible with chemical, defect and strain engineering [30,98], therefore, the range of candidate energy storage systems can be greatly expanded by the AFD-to-FD transition. With reference to the above classifications, the STO/LSMO system, with ultrahigh energy density (307 J/cm 3 ) at a thickness range of 410~710 nm for STO, provides a good example to analyze the AFD-to-FD transition [28,99].…”

Artificial intelligence for search and discovery of quantum materials

“…The most widely used computational method for simulating materials properties is Density Functional Theory (DFT), which has served as the backbone of materials by design in areas such as energy and magnetic materials (see, for example, refs. [39][40][41] ). Yet, DFT is built on several commonly used but essentially uncontrolled approximations.…”