Photonic crystals possessing multiple Weyl points and the experimental observation of robust surface states

• Published in: Nature communications Vol. 7; no. 1; p. 13038
• Main Authors: Chen, Wen-Jie, Xiao, Meng, Chan, C. T.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.10.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/399/1022; 639/766/119/2792; Correspondence; Crystals; Design; Doppler effect; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary); Symmetry; Hong Kong China; China
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13038

Weyl points, as monopoles of Berry curvature in momentum space, have captured much attention recently in various branches of physics. Realizing topological materials that exhibit such nodal points is challenging and indeed, Weyl points have been found experimentally in transition metal arsenide and phosphide and gyroid photonic crystal whose structure is complex. If realizing even the simplest type of single Weyl nodes with a topological charge of 1 is difficult, then making a real crystal carrying higher topological charges may seem more challenging. Here we design, and fabricate using planar fabrication technology, a photonic crystal possessing single Weyl points (including type-II nodes) and multiple Weyl points with topological charges of 2 and 3. We characterize this photonic crystal and find nontrivial 2D bulk band gaps for a fixed k z and the associated surface modes. The robustness of these surface states against k z -preserving scattering is experimentally observed for the first time. To realize Weyl points carrying topological charges higher than one is challenging. Here, Chen et al . report a photonic crystal possessing single and multiple Weyl points with topological charges of two and three using planar fabrication technology.