Edge Modes, Degeneracies, and Topological Numbers in Non-Hermitian Systems
Bliokh, Konstantin Y.
Chong, Yi Dong
Date of Issue2017
School of Physical and Mathematical Sciences
Centre for Disruptive Photonic Technologies
We analyze chiral topological edge modes in a non-Hermitian variant of the 2D Dirac equation. Such modes appear at interfaces between media with different “masses” and/or signs of the “non-Hermitian charge.” The existence of these edge modes is intimately related to exceptional points of the bulk Hamiltonians, i.e., degeneracies in the bulk spectra of the media. We find that the topological edge modes can be divided into three families (“Hermitian-like,” “non-Hermitian,” and “mixed”); these are characterized by two winding numbers, describing two distinct kinds of half-integer charges carried by the exceptional points. We show that all the above types of topological edge modes can be realized in honeycomb lattices of ring resonators with asymmetric or gain-loss couplings.
Physical Review Letters
© 2017 American Physical Society (APS). This paper was published in Physical Review Letters and is made available as an electronic reprint (preprint) with permission of American Physical Society (APS). The published version is available at: [http://dx.doi.org/10.1103/PhysRevLett.118.040401]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.