Symmetry-Enforced Dirac Points and Quad-Helicoid Topological Surface States in a Nonsymmorphic Phono (IMAGE)

Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS

Symmetry-Enforced Dirac Points and Quad-Helicoid Topological Surface States in a Nonsymmorphic Phono

Caption

Schematics of the bcc unit (left panel) of the phononic crystal and its (010) surface (right panel) featured with two glide mirrors Gx and Gz. b, 3D bcc BZ and its (010) surface BZ. The coloured spheres highlight the bulk Dirac points with equal frequency and their projections onto the surface BZ. c, Bulk bands simulated along several high-symmetry directions. d, Schematic of the quad-helicoid surface state dispersions (colour surfaces), where the grey cone labels the projection of bulk states. e, Surface bands simulated along a circular momentum loop of radius 0.4π/a (as shown in f) centred at P . The shadow regions indicate the projected bulk states. (f) 3D plot of the surface dispersion simulated in the first quadrant of the surface BZ. Bulk band projections are not shown for clarity.

Credit

BY Xiangxi Cai, Liping Ye, Chunyin Qiu, Meng Xiao, Rui Yu, Manzhu Ke, Zhengyou Liu

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