SKM 2023 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Plasmonics and Nanooptics I: Fabrication and Application
O 49.4: Vortrag
Mittwoch, 29. März 2023, 11:15–11:30, WIL A317
Topological insulating phase in non-Hermitian plasmonic waveguide arrays — •Helene Wetter1, Stefan Linden1, and Julian Schmitt2 — 1Physikalisches Institut, Universität Bonn, Kreuzbergweg 24, 53115-Bonn, Germany — 2Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115-Bonn, Germany
Arrays of evanescently coupled plasmonic waveguides are a powerful platform to investigate topological properties of one-dimensional lattices. The underlying principle is the mathematical equivalence between the single-particle tight-binding Schrödinger equation and the coupled mode equation. By tailoring the loss distribution, we utilize non-Hermiticity as a new approach to induce topological phases in otherwise trivial systems. We employ dielectric loaded surface plasmon polariton waveguides fabricated on a thin gold film. Additional losses are introduced to specific waveguides by deposition of a thin layer of chromium below the respective waveguides. Considering a unit cell of four waveguides, a topologically nontrivial lattice can be created by adding an equal amount of losses to the two central waveguides of the unit cell. In contrast, losses on either the first or the last two waveguides of a unit cell correspond to a trivial lattice. Using leakage radiation microscopy, we observe localized states at the edge of the nontrivial lattice (edge mode) as well as at the interface between the nontrivial and the trivial lattice (interface mode). Conversely, the trivial lattice does not provide a localized edge mode. Thus, the topological properties can solely be controlled by the design of the unit cell.