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Nat Commun. 2018 Jan 26;9(1):403. doi: 10.1038/s41467-017-02813-5.

Configurable topological textures in strain graded ferroelectric nanoplates.

Author information

1
Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 34141, Republic of Korea.
2
Department of Materials Modelling and Characterization, Korea Institute of Materials Science, Changwon, Gyeongnam, 51508, Republic of Korea.
3
Department of Materials Science and Engineering, Pusan National University, Geumjeong-gu, Busan, 46241, Republic of Korea.
4
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
5
Pohang Accelerator Laboratory, POSTECH, Pohang, Gyeongbuk, 37673, Republic of Korea.
6
Department of Materials Science and Engineering, POSTECH, Pohang, Gyeongbuk, 37673, Republic of Korea.
7
Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA.
8
Department of Physics, University of California, Berkeley, CA, 94720, USA.
9
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
10
Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 34141, Republic of Korea. chyang@kaist.ac.kr.
11
KAIST Institute for the NanoCentury, KAIST, Yuseong-gu, Daejeon, 34141, Republic of Korea. chyang@kaist.ac.kr.

Abstract

Topological defects in matter behave collectively to form highly non-trivial structures called topological textures that are characterised by conserved quantities such as the winding number. Here we show that an epitaxial ferroelectric square nanoplate of bismuth ferrite subjected to a large strain gradient (as much as 105 m-1) associated with misfit strain relaxation enables five discrete levels for the ferroelectric topological invariant of the entire system because of its peculiar radial quadrant domain texture and its inherent domain wall chirality. The total winding number of the topological texture can be configured from - 1 to 3 by selective non-local electric switching of the quadrant domains. By using angle-resolved piezoresponse force microscopy in conjunction with local winding number analysis, we directly identify the existence of vortices and anti-vortices, observe pair creation and annihilation and manipulate the net number of vortices. Our findings offer a useful concept for multi-level topological defect memory.

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