Tsuneya Yoshida

Deptpartment of Physics,
University of Tsukuba
Japan

Symmetry-protected exceptional rings and surfaces

One of the remarkable phenomena in non-Hermitian systems is the emergence of exceptional points where the Hamiltonian becomes non-diagonalizable. Recently, it has been elucidated that exceptional points can be regarded as topological degeneracies in the bulk[1]. The above progress implies that a variety of exceptional points lie in the non-Hermitian systems. In this talk, we show symmetry results in novel non-Hermitian degeneracies, which we call symmetry-protected exceptional rings (SPER) or symmetry-protected exceptional surfaces[2]. Furthermore, we demonstrate that they emerge not only quantum systems but also classical systems described by Newton’s equation[3]. If time allows, we will briefly mention our recent work on non-Hermitian fractional quantum Hall states[4].

[1] H. Shen, B. Zhen, and L. Fu, Phys. Rev. Lett. 120, 146402 (2017).
[2] T. Yoshida, R. Peters, Y. Hatsugai, and N. Kawakami, Phys. Rev. B 99, 121101 (2019).
[3] T. Yoshida and Y. Hatsugai, Phys. Rev. B 100, 054109 (2019).
[4] T. Yoshida, K. Kudo, and Y. Hatsugai, arXiv:1907.07596.