Lattice-matched heterojunctions between topological and normal insulators: A first-principles study

Abstract

Gapless boundary modes at the interface between topologically distinct regions are one of the most salient manifestations of topology in physics. Metallic boundary states of time-reversal-invariant topological insulators (TIs), a realization of topological order in condensed matter, have been of much interest not only due to such a fundamental nature, but also due to their practical significance. These boundary states are immune to backscattering and localization owing to their topological origin, thereby opening up the possibility to tailor them for potential uses in spintronics and quantum computing. The heterojunction between a TI and a normal insulator (NI) is a representative playground for exploring such a topologically protected metallic boundary state and expected to constitute a building block for future electronic and spintronic solid-state devices based on TIs. Here, we report a first-principles study of two experimentally realized lattice-matched heterojunctions between TIs and NIs, Bi2Se3(0001)/InP(111) and Bi2Te3(0001)/BaF2 (111). We evaluate the band offsets at these interfaces from many-body perturbation theory within the GW approximation as well as density-functional theory. Furthermore, we investigate the topological interface states, demonstrating that at these lattice-matched heterointerfaces they are strictly localized and their helical spin textures are as well preserved as those at the vacuum-facing surfaces. These results taken together may help in designing devices relying on spin-helical metallic boundary states of TIs.

Importance of van der Waals interactions for ab initio studies of topological insulators

“…The results reproduce salient features of the electronic spectra in bulk and at surfaces, although there is some debate about whether many body corrections are necessary to obtain both the correct magnitude of the gap and its character (direct vs indirect) [14,17,18]. In the same spirit, existing studies of interfaces either consider lattice matched cases [19] or make a priori assumptions about structural changes at the boundary, such as fixing the inter-QL distance to its experimental value [20].…”

Topological Proximity-Induced Dirac Fermion in Two-Dimensional Antimonene

“…For instance, it has been predicted that a hybrid structure made of a 3D TI and a superconductor can produce a superconducting proximity effect at the interface, which might lead to the emergence of two-dimensional (2D) topological superconductivity hosting Majorana fermions. , In graphene transferred on 3D TI, a strong proximity effect can induce opening of the band gap and strong spin–orbit coupling (SOC), which leads to a strong tunability and suppression of the spin signal and lifetime. , There has been some research on the topological proximity effect between a normal insulator and a topological insulator (NI/TI). Previous calculations and experiments have indicated that a Dirac state exists at the NI/TI interface because of the proximity effect caused by TIs. − In addition, predictions of such an interaction with non-topological states at the NI/TI interface might result in vertical twinning of the Dirac cone; the non-topological states can acquire spin texture without magnetic doping . The group-V single-element monolayer with a band gap ranging from 0.36 to 2.62 eV on a TI is an ideal platform for the study of the topological proximity effect at a NI/TI interface. , In particular, the band structure on a 2D NI/3D TI can be directly probed with angle-resolved photoemission spectra (ARPES).…”

Topological phase transition at the interface of a topological with a conventional insulator

“…There have been many efforts recently to understand the phenomena at the interface of a TI with different materials, e.g. metals, conventional insulators [10,11], as well as other materials [4,12,13]. It has also been demonstrated experimentally that the surface bands of the TI can be modulated by modifications of the surface [5].…”