10/26
2023
Seminar
- Title题目 Quantized fractional corner charge in insulators with various crystal shapes in three dimensions
- Speaker报告人 Shuichi Murakami （东京工业大学）
- Date日期 2023年10月26日 10:00
- Venue地点 北楼322
Abstract摘要
In some insulators, corner charges are fractionally quantized, due to the topological invariant called a filling anomaly. The previous theories of fractional corner charges have been mostly limited to two-dimensional systems [1,2]. In three dimensions, only limited cases have been studied [3]. In this study, we derive formulas for the filling anomaly and the corner charge in general crystal shapes in three dimensions [4,5]. We discuss that the quantized corner charge requires the crystal shapes to be vertex-transitive polyhedra, where all the vertices are equivalent by symmetry. We exhaustively study crystal shapes within this class, and show that the formula of the filling anomaly is universally given by the difference between electronic and ionic charges at the Wyckoff position 1a. The fractional corner charges appear by equally distributing the filling anomaly to all the corners of the crystal. We also derive the k-space formulas for the fractional corner charge. In some cases, the corner charge is not determined solely from the irreps at high-symmetry k-points. In such cases, we introduce a new Z2 topological invariant to determine the corner charge [5].
[1] W. A. Benalcazar, T. Li, and T. L. Hughes, Phys. Rev. B 99, 245151 (2019).
[2] R. Takahashi, T. Zhang, and S. Murakami, Phys. Rev. B 103, 205123 (2021).
[3] H. Watanabe and H. C. Po, Phys. Rev. X 11, 041064 (2021).
[4] K. Naito, R. Takahashi, H. Watanabe, and S. Murakami, Phys. Rev. B 105, 045126 (2022).
[5] H. Wada, K. Naito, S. Ono, K. Shiozaki and S. Murakami, preprint (2023)
报告人简介：
Prof. Shuichi Murakami obtained his Ph. D.(1999) degree from the University of Tokyo. He moved to Tokyo Institute of Technology as an associate professor in 2007 and became a professor in the Department of Physics and in Materials Research Center for Element Strategy in 2012. He has been working on theories of spintronics and topological phenomena in condensed matter physics. He received various prizes, including Sir Martin Wood Prize in 2010, IBM Japan Science Prize in 2011, JSPS Prize in 2012, and APS Fellow in 2017.
邀请人：
张田田 副研究员
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