Phase diagram for the ladder model of the dimerized Kitaev chains as a function of the dimerization and the chemical potential with chain numbers n along the y axis. The energy unit is t_x, and we have taken θ = π/2, |Δ_x| = |Δ_y| = 0.8t_x, and t_y = t_x. Blue region denotes the topologically nontrivial phase (ℳ = −1), and yellow region denotes the topologically trivial phase (ℳ = +1). The red dashed lines guide the value of η = 0.2t_x. (a) n = 2; (b) n = 3; (c) n = 4; (d) n = 5; (e) n = 6; (f) n = 7.