Stabilizing hidden room-temperature ferroelectricity via a metastable atomic distortion pattern
Jeong Rae Kim, Jinhyuk Jang, Kyoung‐June Go, Se Young Park, Chang Jae Roh, John Bonini, Jinkwon Kim, Han Gyeol Lee, Karin M. Rabe, Jong Seok Lee, Si‐Young Choi, Tae Won Noh, Daesu Lee
Abstract
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 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.