Abstract
We report the bulk and surface electronic properties and spin polarization of a rich family of Sn-based ternary topological insulators studied by means of first-principles calculations within the framework of density functional theory. These compounds exist with the following stoichiometries: $\mathrm{Sn}{X}_{2}{\mathrm{Te}}_{4},\phantom{\rule{0.16em}{0ex}}\mathrm{Sn}{X}_{4}{\mathrm{Te}}_{7}$, and ${\mathrm{SnBi}}_{6}{\mathrm{Te}}_{10}$ ($X$ = Sb and Bi). Where a septuple layer or a quintuple layer and septuple layer blocks alternate along the hexagonal axis. We reveal that the bulk band gap in these compounds is about 100 meV and recognize a strong dependence of the spin polarization on the cleavage surface. The calculated spin polarization reaches 85% in some cases, that is one of the highest predicted values hitherto. Since the electron spin polarization is a relevant parameter for spintronics technology, this new family is suitable for applications within this field.
Highlights
Spin-polarized carriers and manipulation of spin currents are essential requirements for spin-based electronics realization
Since the bulk and surface electronic structures of these topological insulators (TIs) have been already studied, we adduce in detail here only quantitative analysis of the spin polarization of the topological surface state (SS) which was not reported for these compounds
It has been established that Sn-based ternary compounds SnX2Te4, SnX4Te7, and SnBi6Te10 (X = Sb, Bi) are 3D Z2 topological insulators while SnSb6Te10 is not
Summary
Spin-polarized carriers and manipulation of spin currents are essential requirements for spin-based electronics realization. Since time-reversal symmetry is preserved in this type of TI, the surface state is protected from backscattering in the presence of weak perturbations [1,2,3,5] Owed to these unique properties, these materials are very attractive for spintronics applications [1,2,3,4,10]. Various families of 3D TIs that hold high spin-polarized SSs have been exhaustively studied, such as the binary Bi2Te3, Bi2Se3, and Sb2Te3 [4,12,13,14,15,16,17,18,19,20,21] These compounds are strong TIs with the topological SS (TSS) mostly located in the first atomic layers adjacent to the vacuum side. Bi2Se3 possessing a rather wide bulk energy gap supporting the Dirac state was predicted to have only 50% of spin polarization in the TSS, which turned in good agreement with recent experiment [23]
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