Fig. 1: Structural chirality and topological quantum chirality in CoSi and RhSi. | Nature

Fig. 1: Structural chirality and topological quantum chirality in CoSi and RhSi.

From: Topological chiral crystals with helicoid-arc quantum states

Fig. 1

a, Chiral crystal structure of XSi (X = Co, Rh), space group P213, number 198. b, Single-crystal X-ray diffraction precession pattern of the (0kl) planes of CoSi at 100 K. The resolved spots confirm space group P213 with lattice constant a = 4.43 Å. c, Three-dimensional Fourier map showing the electron density in the CoSi structure. The colour indicates electron density, with yellow corresponding to electron-rich regions and white to electron-poor regions. d, Ab initio calculation of the electronic bulk band structure along high-symmetry lines. A threefold-degenerate topological chiral fermion is predicted at Γ and a fourfold topological chiral fermion at R, with Chern numbers +2 and −2, respectively. The highest valence (blue) and lowest conduction (red) bands fix a topologically non-trivial energy window (green dashed lines). e, Bulk BZ and (001) surface BZ with high-symmetry points; the predicted chiral fermions (red and blue spheres) are marked. f, Ab initio calculation of the surface spectral weight on the (001) surface for CoSi, with the (001) surface BZ marked (red box). The predicted bulk chiral fermions project onto \(\bar{{\rm{\Gamma }}}\) and \(\bar{{\rm{M}}}\), connected by a pair of topological Fermi arcs extending diagonally across the surface BZ. The colour bar limits correspond to high (H) and low (L) electron density.

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