Band structure engineering of topological insulator heterojunctions

Abstract

We investigate the topological surface states in heterostructures formed from a three-dimensional topological insulator (TI) and a two-dimensional insulating thin film, using first-principles calculations and the tight-binding method. Utilizing a single Bi or Sb bilayer on top of the topological insulators Bi 2 Se 3 , Bi 2 Te 3 , Bi 2 Te 2 Se, and Sb 2 Te 3 , we find that the surface states evolve in very peculiar but predictable ways. We show that strong hybridization between the bilayer and TI substrates causes the topological surface states to migrate to the top bilayer. It is found that the difference in the work function of constituent layers, which determines the band alignment and the strength of hybridization, governs the character of newly emerged Dirac states.

Understanding the Giant Enhancement of Exchange Interaction in Bi2Se3−EuS Heterostructures

“…The X-shape band around -0.3 eV in the vicinity of the Γ point (high-energy TSS) results from the rehybridization between TSS and quantumwell states of Bi 2 Se 3 ( Fig. S6 in SM), which frequently appears in TI heterostructures [25,39,40]. This Dirac state localizes mostly in the second QL from the interface [30] and quickly merges into the bulk bands away from the Brillouin zone center.…”

Tip-induced superconductivity coexisting with preserved topological properties in line-nodal semimetal ZrSiS

“…Such discovery is particularly important because ZrSiS is known to show a linear band dispersion over a large energy range ∼ 2 eV 17 whereas the linear extent for most of the other topological materials is limited up to few hundred meV from respective Dirac points. 18,19 This makes the topological properties of ZrSiS extremely robust against carrier doping, variation of stochiometry and other external perturbative effects thereby implying that when a superconducting phase is realized on ZrSiS point contacts, the topological properties of ZrSiS are not expected to be destroyed merely by the presence of a metallic tip forming the point contacts. Therefore, the superconducting phase realized on ZrSiS does not emerge at the expense of the topological nature of ZrSiS.…”

Spinodal Superlattices of Topological Insulators

“…This is consistent with previous studies of TI heterostructures, which show that depending on the interaction strength at the interface, the spatial position of the Dirac states can shift away from the interface. 25,86,87 The orbital character of the B 1 and B 2 bands at Γ are mainly p z , consistent with surface states of TlBiSe 2 , and different from the p xy orbital character of the valence band maximum and conduction band minimum of the bulk (see Supplementary Information). Due to the spatial shift of the B 2 state, the total charge density at the Dirac-like point is distributed all over the material instead of accumulating at the interfaces (Figure 2(c)).…”

“…These types of bands are reported for TI heterostructures and are described as mixed-character bands. 87,89 Thusly, instead of two metallic channels, only one metallic channel arises, which includes the entire TlBiSe 2 region. The upper and lower branches of the Dirac-like points have opposite spin polarization (Figure 3(c-e), insets), indicating that they are topologically protected.…”