2017/06/15 by Fei Gao, Haoran Xue, Zhaoju Yang +7 · 1 citation
Materials Science · Physics and Astronomy · #Condensed matter physics #Degenerate energy levels #Lattice (music) #Metamaterials and Metasurfaces Applications #Photonic Crystals and Applications #Photonic crystal #Physics #Polarization (electrochemistry) #Quantum mechanics #Scattering #Topological Materials and Phenomena #Topology (electrical circuits) #Transverse plane #cond-mat.mes-hall #physics.optics
paper · pdf · doi:10.1038/nphys4304
19 pages, 4 figures
arxiv created 2017/06/15 · openalex created_date 2017/06/23 · openalex publication_date 2017/11/13 · arxiv updated 2018/03/14 · openalex updated_date 2026/08/05
Recently discovered valley photonic crystals (VPCs) mimic many of the unusual properties of two-dimensional gapped valleytronic materials such as bilayer graphene or MoS2. Of the utmost interest to optical communications is their ability to support topologically protected chiral edge (kink) states at the internal domain wall between two VPCs with spectrally overlapping bandgap zones and opposite half-integer valley-Chern indices. We experimentally demonstrate the robustness of the kink states in VPCs that support degenerate transverse-electric-like (TE) and transverse-magnetic-like (TM) topological phases, thus enabling polarization multiplexing in a single topological waveguide. The propagation direction of the kink states is locked to the valleys of the reverse Brave lattice and, therefore, cannot be reversed in the absence of inter-valley scattering. At the intersection between the internal domain wall and the external edge separating the VPCs from free space, the kink states are shown to exhibit >97% out-coupling efficiency into directional free-space beams. This constitutes the first experimental demonstration of meron-like valley-projected topological phases with half-integer valley-Chern indices.