Two-Dimensional Topological Insulator Phase in Epitaxial SnTe(111) Films

SnTe is a topological crystalline insulator (TCI) with surface states protected by the mirror symmetry. Theoretical studies predict that SnTe(111) films can host a two-dimensional (2D) topological insulator (TI) phase over a specific thickness range. In this work, we employ molecular beam epitaxy (MBE) to grow SnTe(111) films on InP(111) substrates and perform angle-resolved photoemission spectroscopy measurements. We observe well-defined quantum well states, whose quantized subbands evolve systematically with film thickness. By combining density functional theory (DFT) calculations, we demonstrate a 2D TI phase in SnTe (111) films with thicknesses of 8-15 bilayers. These findings establish SnTe (111) films as a tunable platform for exploring and controlling different topological phases via varying thickness, opening new avenues for topological electronics and device applications.