Tunable Nanoscale Evolution and Topological Phase Transitions of a Polar Vortex Supercrystal
Cheng Dai, Vladimir A. Stoica, Sujit Das, Zijian Hong, Lane W. Martin, R. Ramesh, J. W. Freeland, Haidan Wen, Venkatraman Gopalan, Long‐Qing Chen
Abstract
Abstract Understanding the phase transitions and domain evolutions of mesoscale topological structures in ferroic materials is critical to realizing their potential applications in next‐generation high‐performance storage devices. Here, the behaviors of a mesoscale supercrystal are studied with 3D nanoscale periodicity and rotational topology phases in a PbTiO 3 /SrTiO 3 (PTO/STO) superlattice under thermal and electrical stimuli using a combination of phase‐field simulations and X‐ray diffraction experiments. A phase diagram of temperature versus polar state is constructed, showing the formation of the supercrystal from a mixed vortex and a‐ twin state and a temperature‐dependent erasing process of a supercrystal returning to a classical a ‐twin structure. Under an in‐plane electric field bias at room temperature, the vortex topology of the supercrystal irreversibly transforms to a new type of stripe‐like supercrystal. Under an out‐of‐plane electric field, the vortices inside the supercrystal undergo a topological phase transition to polar skyrmions. These results demonstrate the potential for the on‐demand manipulation of polar topology and transformations in supercrystals using electric fields. The findings provide a theoretical understanding that may be utilized to guide the design and control of mesoscale polar structures and to explore novel polar structures in other systems and their topological nature.