Published: 12 December 2016, 12:21 | By: Christian Helgert
Together with colleagues from the Technion in Haifa/Israel, the Crete Center for Quantum Complexity and Nanotechnology, the Vienna University of Technology and the Pennsylvania State University, ACP principal scientists Stefan Nolte and Alexander Szameit have just published an original research article titled "Topologically protected bound states in photonic parity-time-symmetric crystals" in Nature Materials (Weimann et al., Nature Mater., doi: 10.1038/nmat4811, 2016).
Abstract: Parity-time (PT)-symmetric crystals are a class of non-Hermitian systems that allow, for example, the existence of modes with real propagation constants, for self-orthogonality of propagating modes, and for uni-directional invisibility at defects. Photonic PT-symmetric systems that also support topological states could be useful for shaping and routing light waves. However, it is currently debated whether topological interface states can exist at all in PT-symmetric systems. Here, we show theoretically and demonstrate experimentally the existence of such states: states that are localized at the interface between two topologically distinct PT-symmetric photonic lattices. We find analytical closed form solutions of topological PT-symmetric interface states, and observe them through fluorescence microscopy in a passive PT-symmetric dimerized photonic lattice. Our results are relevant towards approaches to localize light on the interface between non-Hermitian crystals.