Non-Dirac topological surface states in (SnTe)$_{n\geq2}$(Bi$_2$Te$_3$)$_{m=1}$

TL;DR

This paper reports the discovery of a new type of topological surface states in layered (SnTe)$_{n=2,3}$(Bi$_2$Te$_3$)$_{m=1}$ compounds, characterized by non-Dirac dispersion and tunable carrier velocity.

Contribution

It introduces a novel topological surface state with non-Dirac dispersion in layered compounds combining SnTe and Bi$_2$Te$_3$, expanding the understanding of topological materials.

Findings

Discovered non-Dirac topological surface states in layered compounds.

Surface state dispersion has two linear sections with different slopes.

External electric field can switch the velocity of topological carriers.

Abstract

A new type of topological spin-helical surface states was discovered in layered van der Waals bonded (SnTe)$_{n=2,3}$(Bi$_2$Te$_3$)$_{m=1}$ compounds which comprise two covalently bonded band inverted subsystems, SnTe and Bi$_2$Te$_3$, within a building block. This novel topological states demonstrate non-Dirac dispersion within the band gap. The dispersion of the surface state has two linear sections of different slope with shoulder feature between them. Such a dispersion of the topological surface state enables effective switch of the velocity of topological carriers by means of applying an external electric field.