  Twisting the stacking of layered materials leads to rich new physics. A three
dimensional (3D) topological insulator film host two dimensional gapless Dirac
electrons on top and bottom surfaces, which, when the film is below some
critical thickness, will hybridize and open a gap in the surface state
structure. The hybridization gap can be tuned by various parameters such as
film thickness, inversion symmetry, etc. according to the literature. The 3D
strong topological insulator Bi(Sb)Se(Te) family have layered structures
composed of quintuple layers (QL) stacked together by van der Waals
interaction. Here we successfully grow twistedly-stacked Sb2Te3 QLs and
investigate the effect of twist angels on the hybridization gaps below the
thickness limit. We find that the hybridization gap can be tuned for films of
three QLs, which might lead to quantum spin Hall states. Signatures of
gap-closing are found in 3-QL films. The successful in-situ application of this
approach opening a new route to search for exotic physics in topological
insulators.
