Dai Cheng, Stoica Vladimir Alexandru, Das Sujit, Hong Zijian, Martin Lane W, Ramesh Ramamoorthy, Freeland John W, Wen Haidan, Gopalan Venkatraman, Chen Long-Qing
Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA, 16802, USA.
Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA.
Adv Mater. 2022 Mar;34(11):e2106401. doi: 10.1002/adma.202106401. Epub 2022 Feb 3.
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 /SrTiO (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.
了解铁电材料中中尺度拓扑结构的相变和畴演化对于实现其在下一代高性能存储设备中的潜在应用至关重要。在此，利用相场模拟和X射线衍射实验相结合的方法，研究了具有三维纳米尺度周期性和旋转拓扑相的中尺度超晶体在PbTiO₃/SrTiO₃（PTO/STO）超晶格中在热和电刺激下的行为。构建了温度与极化状态的相图，显示了超晶体从混合涡旋和a孪晶状态形成，以及超晶体回到经典a孪晶结构的温度依赖性擦除过程。在室温下的面内电场偏置下，超晶体的涡旋拓扑不可逆地转变为一种新型的条纹状超晶体。在面外电场下，超晶体内的涡旋经历拓扑相变成为极性斯格明子。这些结果证明了利用电场对超晶体中的极性拓扑和转变进行按需操纵的潜力。这些发现提供了一种理论理解，可用于指导中尺度极性结构的设计和控制，并探索其他系统中的新型极性结构及其拓扑性质。
