Modification of the Hybridization Gap by Twisted Stacking of Quintuple Layers in a Three-Dimensional Topological Insulator Thin Film

Abstract

Twisting the stacking of layered materials leads to rich new physics. A three-dimensional topological insulator film hosts 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 and inversion symmetry, according to the literature. The three-dimensional strong topological insulator Bi(Sb)Se(Te) family has layered structures composed of quintuple layers (QLs) 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. It is found that the hybridization gap can be tuned for films of three QLs, which may lead to quantum spin Hall states. Signatures of gap-closing are found in 3-QL films. The successful in situ application of this approach opens a new route to search for exotic physics in topological insulators.

Recent Advances in Moiré Superlattice Structures of Twisted Bilayer and Multilayer Graphene

“…For instance, recent successful synthesis of twistedly stacked Sb 2 Te 3 quintuple layers was reported by Zhou et al, where they found hybridized gaps to be a potential reason for the appearance of quantum spin Hall states. [156] Moreover, the orientations of each layer will be an essential knob to adjust macroscopic properties of the whole system, which endows van der Waals materials with more possibilities to play an adjustable role in future applications. Recently, it is shown that when there are two small independent twist angles in twisted trilayer graphene, zero-resistance domes appear in transport measurements, which is suspect of superconductivity.…”