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Title: Topologically protected refraction of robust kink states in valley photonic crystals
Authors: Gao, Fei
Xue, Haoran
Yang, Zhaoju
Lai, Kueifu
Yu, Yang
Lin, Xiao
Chong, Yidong
Shvets, Gennady
Zhang, Baile
Keywords: Photonic Crystals
Issue Date: 2018
Source: Gao, F., Xue, H., Yang, Z., Lai, K., Yu, Y., Lin, X., . . . Zhang, B. (2018). Topologically protected refraction of robust kink states in valley photonic crystals. Nature Physics, 14(2), 140-144. doi:10.1038/nphys4304
Series/Report no.: Nature Physics
Abstract: Recently discovered1,2 valley photonic crystals (VPCs) mimic many of the unusual properties of two-dimensional (2D) gapped valleytronic materials3,4,5,6,7,8,9. Of the utmost interest to optical communications is their ability to support topologically protected chiral edge (kink) states3,4,5,6,7,8,9 at the internal domain wall between two VPCs with opposite valley-Chern indices. Here we experimentally demonstrate valley-polarized kink states with polarization multiplexing in VPCs, designed from a spin-compatible four-band model. When the valley pseudospin is conserved, we show that the kink states exhibit nearly perfect out-coupling efficiency into directional beams, through the intersection between the internal domain wall and the external edge separating the VPCs from ambient space. The out-coupling behaviour remains topologically protected even when we break the spin-like polarization degree of freedom (DOF), by introducing an effective spin–orbit coupling in one of the VPC domains. This also constitutes the first realization of spin–valley locking for topological valley transport.
ISSN: 1745-2473
DOI: 10.1038/nphys4304
Rights: © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. This paper was published in Nature Physics and is made available with permission of Macmillan Publishers Limited, part of Springer Nature.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SPMS Journal Articles

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