Strain-induced two-dimensional topological crystalline insulator in bilayer SnTe.

Topological crystalline insulators host topological phases of matter protected by crystal symmetries. Despite the prediction of a two-dimensional topological crystalline insulator, materials challenges have, to the best of our knowledge, thus far prevented its experimental realization. Here we report the growth and characterization of bilayer SnTe on the 2H-NbSe2 substrate by molecular beam epitaxy and scanning tunneling microscopy. We experimentally observe bilayer SnTe experiences compressive strain and exhibits two anticorrelated, periodically modulated pairs of conducting edge states within a large band gap exceeding 0.2 eV. We identify these states as topological edge states through first-principles calculations. Finally, we experimentally probe the coupling of adjacent topological edge states and demonstrate the resulting energy shift driven by a combination of electrostatic interactions and tunneling coupling. Our work opens the door to investigations of tunable two-dimensional topological states, of potential impact for spintronics and nanoelectronics applications at room temperature.