Two- and three-dimensional topological phases in BiTeX compounds

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 Bi2Te2I2 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 Bi2Te2I2 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 Bi2Te2I for which the stacking of nontrivial SLs in a three-dimensional (3D) limit results in a strong topological insulator (TI) phase, a 3D TI Bi2Te2Br2 is formed by trivial SLs. For the last material of the BiTeX (X=I,Br,Cl) series, BiTeCl, both 2D and 3D centrosymmetric phases are characterized by topologically trivial band structure.
This work was supported by the Spanish Ministry of Economy and Competitiveness MINECO (Project No. FIS2016-76617-P), Saint Petersburg State University (Grant No. 15.61.202.2015), Tomsk State University competitiveness improvement programme (Project No. 8.1.01.2017), and RFBR (Grant No. 15-02-02717-a).