title: Observation of a Topological Transition in the Bulk of a Non-Hermitian System.
abstract: We present the first experimental observation of a topological transition in a non-Hermitian system. In contrast to standard methods for examining topological properties, which involve probing edge (or surface) states, we monitor the topological transition by employing bulk dynamics only. The system is composed of a lattice of evanescently coupled optical waveguides, and non-Hermitian behavior is engineered by inducing bending loss by spatially "wiggling" every second waveguide.
authors.affiliation: Institute of Applied Physics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Zeuner
authors.affiliation: Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Mikael C
authors.initials: MC
authors.lastname: Rechtsman
authors.affiliation: Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Yonatan
authors.initials: Y
authors.lastname: Plotnik
authors.affiliation: Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Lumer
authors.affiliation: Institute of Applied Physics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Nolte
authors.affiliation: The Niels Bohr International Academy, Niels Bohr Institute, 2100 Copenhagen, Denmark.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Rudner
authors.affiliation: Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Mordechai
authors.initials: M
authors.lastname: Segev
authors.affiliation: Institute of Applied Physics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Szameit