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記
日時：２０１９年０５月０８日（水）１３時３０分〜
場所：東京大学 生産技術研究所 千葉実験所 研究実験棟Ｉn210号室
道程：http://hatano-lab.iis.u-tokyo.ac.jp/access.html
講師：吉田恒也さん（筑波大）
演題：Symmetry-protection of non-Hermitian degeneracies for correlated systems
要旨：
In this decade, topological phases have attracted much interest. As the results of extensive analysis, a variety of topological insulators/superconductors have been reported which arise from interplay between symmetry and the topological properties.
In parallel to the above progress, non-Hermitian systems [1] have been pioneered as new platforms of topological physics [2]. Notably, the platforms of non-Hermitian topological physics extend to a wide range of systems; cold atoms out of equilibrium [2], correlated systems in equilibrium [3,4] etc. As this field has been pioneered very recently, many significant issues remain open questions. One of them is the interplay between symmetry and exceptional points which are topological non-Hermitian degeneracies.
We here address this issue by analyzing correlated systems. Our analysis discovers symmetry-protected non-Hermitian degeneracies [5]. By employing the dynamical mean-field theory, we demonstrate the emergence of symmetry-protected exceptional rings for a honeycomb Hubbard model. If time allows, we also show the emergence of symmetry-protected exceptional rings for classical systems [6], indicating the ubiquity of the symmetry-protected non-Hermitian degeneracies.
参考文献
[1] N. Hatano and D. R. Nelson, Phys. Rev. Lett. 77 570 (1996).
[2] Z. Gong, Y. Ashida, K. Kawabata, K. Takasan, S. Higashikawa, and M. Ueda, Phys. Rev. X 8 031079 (2018).
[3] V. Kozii and L. Fu, arXiv: 1708.05841.
[4] T. Yoshida, R. Peters, and N. Kawakami, Phys. Rev. B 98 035141 (2018).
[5] T. Yoshida, R. Peters, N. Kawakami, and Y. Hatsugai, Phys. Rev. B 99 035141 (2019).
[6] T. Yoshida and Y. Hatsugai, submitted.
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李 宰河
〒277-8574 千葉県柏市柏の葉5-1-5
東京大学生産技術研究所
e-mail: lee@iis.u-tokyo.ac.jp
Tel: 04-7136-6977
Fax: 04-7136-6978
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