Figure 1. ARPES results on 20 QLs Bi₂Se₃, 20 QLs Bi₂Te₃ and 1 QL Bi₂Se₃/19 QLs Bi₂Te₃ heterostructure thin films.

(a) 20 QLs Bi₂Se₃ (b) 20 QLs Bi₂Te₃ (c) 1 QL Bi₂Se₃/19 QLs Bi₂Te₃ heterostructure thin film measured along the K-Γ-Κ direction, the yellow line indicates the Fermi level, and the red and blue lines indicate the surface state. The lower figures (d) to (f) are the corresponding momentum distribution curves, the blue lines indicates the Fermi level.