Fig. 3.

(A and B) Two types of 1D bismuth rods that preserve the twofold rotation symmetry $2_{\left[1\overline{1}0\right]}$. These rods are periodic along the $\left[1\overline{1}0\right]$ axis but finite sized within the plane that is perpendicular to $\left[1\overline{1}0\right]$. In the first rod (A), the side surfaces are the (111) and $\left(11\overline{2}\right)$ surfaces and the cross-section is a rectangle. (C and D) Energy dispersions of rods 1 and 2. The topological hinge states are marked by red lines. (E and F) Real-space distributions of the hinge states of rods 1 and 2.