Modification of the hybridization gap by twisted stacking of quintuple layers in a three dimensional topological insulator thin film

TL;DR

This study demonstrates that twisting the stacking of quintuple layers in a 3D topological insulator thin film can modulate the hybridization gap, potentially enabling new quantum states like the quantum spin Hall effect.

Contribution

It introduces a novel method of tuning the hybridization gap in topological insulator films through twisted stacking of quintuple layers, expanding control over their electronic properties.

Findings

Hybridization gap can be tuned by twist angles in 3-QL films.

Signatures of gap-closing observed in 3-QL films.

Twisted stacking opens new avenues for exploring exotic physics in topological insulators.

Abstract

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.