Two- and three-dimensional topological phases in BiTeX compounds

S V Eremeev,E V Chulkov,I A Nechaev

doi:10.1103/physrevb.96.155309

Abstract

Recently, it was shown that quantum spin Hall insulator phase with a gap wide enough for practical applications can be realized in the ultrathin films constructed from two inversely stacked structural elements of trivial band insulator BiTeI. Here, we study the edge states in nanoribbons made of the ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}{\mathrm{I}}_{2}$ sextuple layer (SL) and the electronic structure of the SL deposited on the natural BiTeI substrate as well as sandwiched between two thick BiTeI films. We show that the ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}{\mathrm{I}}_{2}$ SL keeps nontrivial topological properties. We also demonstrate that ultrathin centrosymmetric films constructed in a similar manner from related material BiTeBr are trivial band insulators up to five-SL film thickness. In contrast to ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}{\mathrm{I}}_{2}$ for which the stacking of nontrivial SLs in a three-dimensional (3D) limit results in a strong topological insulator (TI) phase, a 3D TI ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}{\mathrm{Br}}_{2}$ is formed by trivial SLs. For the last material of the $\mathrm{BiTe}X$ ($X=\text{I}$,Br,Cl) series, BiTeCl, both 2D and 3D centrosymmetric phases are characterized by topologically trivial band structure.

Highlights

Starting from the theoretical predictions by Kane and Mele [1] and Bernevig et al [2,3], the Z2 two-dimensional topological insulator (2D TI) or the quantum spin Hall insulator (QSHI) phase, in which spin-helical gapless edge states counterpropagate along the boundary with opposite spins, providing quantum spin Hall effect (QSHE) [1], attracts considerable attention of researchers
It was shown that quantum spin Hall insulator phase with a gap wide enough for practical applications can be realized in the ultrathin films constructed from two inversely stacked structural elements of trivial band insulator BiTeI
By using first-principles calculations we have examined the topologically protected edge states and topologically trivial Rashba-split spin-polarized dangling bond states that emerged at the different edges of the 2D topological insulator Bi2Te2I2 of one-sextuple-layer thickness

Summary

Introduction

Starting from the theoretical predictions by Kane and Mele [1] and Bernevig et al [2,3], the Z2 two-dimensional topological insulator (2D TI) or the quantum spin Hall insulator (QSHI) phase, in which spin-helical gapless edge states counterpropagate along the boundary with opposite spins, providing quantum spin Hall effect (QSHE) [1], attracts considerable attention of researchers. After experimental observations of the QSHE in HgTe/CdTe and InAs/GaSb quantum wells [4,5], a number of 2D TIs were theoretically proposed [6]. These proposals were mainly based on the layers of bismuth, graphene, or heavy elements analogs of graphene, implying the gap tuning by strain, adatoms deposition, chemical functionalization, growing on substrates, or sandwiching. The goal that remains to be actual so far is to search for robust and fabricated new 2D TIs with a sufficiently large band gap providing edge states accessible to experimental probes at room temperature

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Conclusion