Gao Peng's research group and collaborators in the School of Physics revealed the topological phase transition process of polar sigmon at the atomic scale

Recently, Professor Gao Peng's research group of the Center for Quantum Materials Science of the School of Physics of Peking University and the Electron Microscopy Laboratory has realized the observation of the dynamic evolution and topological phase transition behavior of polar sputterons under the external electric field by using atomic-resolved in situ scanning transmission electron microscopy, revealing its phase change mechanism and interaction, and providing guidance

An analogy to a magnetic semmelon made of spin, polar sigmon made of electrodipoles, was first discovered

The premise of practical electronic device application is that the structure unit has the ability

Gao Peng's research group has long been committed to the study of low-dimensional ferroelectric physics, and recently, they have developed and used in situ local field technology of quantitative atomic image analysis and atomic resolution to apply polar topology with collaborators to the study of polar topology, and have a series of original research results, including the accurate measurement of the polarization distribution of a single polar vortex at the sub-single cell scale (Science Advances 2019, aav4335), according to which the existence of polar anti-vortex in non-polar materials (Nature) was discovered Communications 2021, 12, 2054), and proposed a simple method for manufacturing nano-scale polar vortices using mechanical cutting (Nature Communications 2021, 12, 4620), which further reveals the topological phase transition behavior of polar vortices and flux closed domains under electric and stress fields (Nature Communications 2020, 11 , 1840; PNAS 2020, 117, 18954）

(a) the three-dimensional polarization distribution of polar sigmacks; (b) Polarized distribution of the core section of the Skomyons; (c) The polarization distribution of different planes from top to bottom, namely central divergence, vortex type and central convergence type; (d) Schematic diagram

As shown in Figure e, polar semmelons gradually contract/expand under a positive/negative electric field until they annihilate/merge and a topological phase transition occurs to transform into a mediocre ferroelectric single domain

This work is the first in situ observation of the dynamic evolution behavior of polar sigmon driven by external electric fields at the nano and atomic scales, and proves that the generation, annihilation and size of polar sigmon can be adjusted controllably by using electric fields, which provides rich information

Zhu Ruixue, graduate student of Quantum Materials Science Center of School of Physics, Peking University, Jiang Zhexin, graduate student of School of Aeronautics and Astronautics, Zhejiang University, Zhang Xinxin, joint graduate student of Peking University and Tianjin Polytechnic University, Professor Zhong Xiangli, School of Materials Science and Engineering, Xiangtan University, as co-authors of the paper, Associate Professor Tan Congbing and Gao Peng, School of Physics and Electronic Sciences, Hunan University of Science and Technology, Professor Wang Jie of the School of Aeronautics and Astronautics, Zhejiang University, and Bai Xuedong, researcher of the Institute of Physics, Chinese Academy of Sciences, were co-corresponding authors.