(a) and (d) One-dimensional energy bands for the 2D anisotropic BHZ stripe with Z₂ = 0 and sample width W_y = 300 (a), 60 (d) described in the main text. Panels (b) and (e) show the distributions of edge states in real space corresponding to panels (a) and (d) with fixed Fermi energy. Panels (c) and (f) show schematic plots of helical edge modes corresponding to panels (a) and (d), respectively. The vertical arrows represent the electron spin. In panel (f), the helical edge channels around k_x = π are hybridized due to finite size confinement, leaving one pair of helical edge channels around k_x = 0. Thus, these conducting channels resemble the helical edge channels in a Z₂ = 1 QSHE (g). Panels (c), (f), and (g) are adapted from Ref. [33].