The distribution of velocity matrix elements f ( v x , v y ) = 〈 n 1 ∣ v x ( k ) ∣ n 2 〉 〈 n 2 ∣ v y ( k ) ∣ n 1 〉 on the ( k x , k y ) plane. The in-plane magnetic field is zero. (a) View the distribution versus the k_x. (b) View the distribution versus the k_y. The index n₁ takes the value of two bands below the hybridization gap, and the index n₂ takes the value of two bands above the hybridization gap.