The joint research team of Gao Peng and Li Xinzheng from the School of Physics uses grain boundary engineering to design a universal strategy for atomic-scale flexoelectricity

Grain boundaries are a typical two-dimensional interface

The unique microscopic characteristics of grain boundaries are mainly reflected in two aspects: one is the local chemical composition change at the grain boundary, and the other is the change of the bonding environment at the grain boundary due to the breaking of translational symmetry

In recent years, researcher Gao Peng's research group and collaborators from the Center for Quantum Materials Science and Electron Microscopy Laboratory, School of Physics, Peking University, have used grain boundary engineering to realize the design and regulation of a series of new phases at the atomic scale: the discovery of strontium titanate (SrTiO _{3 )} ) some grain boundaries have two-dimensional antiferrous distorted phases at room temperature ( Physical Review Letters , 2021, 126, 225702); a stable two-dimensional negatively charged gas was constructed using bismuth ferrite (BiFeO _{3 ) grain boundaries (} Science Bulletin , 2021, 66, 771); discovered that strontium ruthenate (SrRuO _{3 )} grain boundaries have spin valve magnetoresistance and revealed its microscopic origin ( National Science Review , 2020, 7, 755); The existence of the curvilinear effect has provided atomic-scale evidence for the first time ( Physical Review Letters, 2018, 120, 267601) .

Recently, Gao Peng, in cooperation with Professor Li Xinzheng from the Institute of Condensed Matter Physics and Materials Physics, School of Physics, Peking University, discovered a universal flexoelectric effect at oxide grain boundaries

Figure a Schematic diagram of the uneven deformation of the unit cell due to symmetry breaking at the grain boundary, and the flexoelectric (Pflexo) induces a net electric dipole moment at the grain boundary; Figure b Atomically resolved LaAlO ₃ grain boundary element distribution; Figure c The all-atom configuration of the LaAlO ₃ grain boundary obtained by the imaging method sensitive to oxygen element ; Fig.

On January 11, 2022, related research results were published online in Nature Communications under the title "Engineering of Atomic-Scale Flexoelectricity at Grain Boundaries " ; Wu Mei, a 2018 doctoral student at the Center for Quantum Materials Science, School of Physics, Peking University, and Zhang Xiaowei, a 2016 doctoral student (now a postdoctoral fellow at the University of Washington) are the co-first authors, and Gao Peng and Li Xinzheng are the co-corresponding authors .

The above research work was supported by the National Natural Science Foundation of China, the Strategic Leading Science and Technology Project of the Chinese Academy of Sciences, the Collaborative Innovation Center for Quantum Matter Science, the Electron Microscopy Laboratory of Peking University, and the High Performance Computing Platform of Peking University