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

• Published in: Nature communications Vol. 11; no. 1; pp. 4944 - 9
• Main Authors: Kim, Jeong Rae, Jang, Jinhyuk, Go, Kyoung-June, Park, Se Young, Roh, Chang Jae, Bonini, John, Kim, Jinkwon, Lee, Han Gyeol, Rabe, Karin M., Lee, Jong Seok, Choi, Si-Young, Noh, Tae Won, Lee, Daesu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 02.10.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 147/137; 639/766/119/544; 639/766/119/996; Artificial neural networks; Calcium titanate; Correlation analysis; Density functional theory; Distortion; Energy; Ferroelectricity; Humanities and Social Sciences; Microscopy; multidisciplinary; Multifunctional materials; Network analysis; Neural networks; Oxides; Oxygen; Perovskites; Physics; Room temperature; Rotating matter; Rotation; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-18741-w

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 CaTiO 3 , 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 CaTiO 3 . 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. Previous studies are limited to modulate oxygen octahedral rotation angles within the same pattern, and engineering the pattern remains a challenge. Here, the authors demonstrate a designed nonequilibrium oxygen octahedral rotation pattern leads to room-temperature ferroelectricity in CaTiO 3 .