Fig. 1: Two-dimensional higher-order topological insulator tight-binding model. | npj Computational Materials

Fig. 1: Two-dimensional higher-order topological insulator tight-binding model.

From: Discovery of higher-order topological insulators using the spin Hall conductivity as a topology signature

Fig. 1

a Bulk band-structure and spin Hall conductivity (\({\sigma }_{xy}^{z}\)) as a function of the Fermi energy. b Eigenvalues for a square flake geometry (open boundary conditions) with 32 × 32 sites. The red circles represent the degenerate corner states, with the inset showing a narrow energy window to emphasize their degeneracy. c Corner states real-space projection. The model parameters of equation (1) are M = 2t = 2ξ = 1 and Δ = 0.25. d Spin Hall conductivity as a function of the model parameters (0 ≤ t ≤ 2), (0 ≤ Δ ≤ 1) and (0 < M ≤ 10). e, f, g Spin Hall conductivity for fixed values of Δ = 0, 0.25, and 0.75, respectively.

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