Energy spectra with respect to μ for the finite chains obtained by numerical diagonalization of the Hamiltonian (15) with parameters: L = 512, θ = π/2, t_y/t_x = 1.0, η/t_x = 0.2, and |Δ_x|/t_x = |Δ_y|/t_x = 0.8. The numbers of chains are (a) n = 2; (b) n = 3; (c) n = 4; (d) n = 5.