title: Topologically Protected Defect States in Open Photonic Systems with Non-Hermitian Charge-Conjugation and Parity-Time Symmetry.
abstract: We show that topologically protected defect states can exist in open (leaky or lossy) systems even when these systems are topologically trivial in the closed limit. The states appear from within the continuum, thus in the absence of a band gap, and are generated via exceptional points (a spectral transition that occurs in open wave and quantum systems with a generalized time-reversal symmetry), or via a degeneracy induced by charge-conjugation symmetry (which is related to the pole transition of Majorana zero modes). We demonstrate these findings for a leaking passive coupled-resonator optical waveguide with asymmmetric internal scattering, where the required symmetries (non-Hermitian versions of time-reversal symmetry, chirality, and charge conjugation) emerge dynamically.
authors.affiliation: Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: Malzard
authors.affiliation: Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom.
authors.forename: Charles
authors.initials: C
authors.lastname: Poli
authors.affiliation: Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom.|Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Schomerus