Ab initioelectronic structure of thallium-based topological insulators

Abstract

We analyze the crystal and electronic structures of Tl-based strong topological insulators TlSbTe 2 , TlSbSe 2 , TlBiTe 2 , and TlBiSe 2 by using first-principles calculation results. The topological nature of these materials is characterized by a single Dirac cone at the point. Aside from the latter robust surface state (SS), we find trivial SSs at (around) the Fermi level for large momenta as well as deep trivial SSs at (around) . The calculated energy cuts show an isotropic shape of the Dirac cone and a simple spin structure of the cone. The strong dependence of electronic structure on both optimization of the chalcogenide atom position in bulk and surface relaxations, as well as the slow convergence of the Dirac cone with respect to the film thickness, are discussed. The situation in the thallides is contrasted with results for isostructural indium compounds InBiTe 2 and InSbTe 2 , the latter not being topological insulators.

Topological Surface States with Persistent High Spin Polarization across the Dirac Point inBi2Te2SeandBi2Se2Miyamoto1, Kimura2, Okuda3 et al. 2012Phys. Rev. Lett.Self Cite9712711View full textAdd to dashboardCite

“…This situation promises an effective spin polarized current under an electric field as well as a substantial suppression of backscattering in the presence of non-magnetic impurities. These new states of matter are also expected to provide fertile ground to realize new phenomena in condensed matter physics, such as a magnetic monopole arising from the topological magnetoelectric effect and Majorana fermions hosted by hybrids with superconductors [5,6].A number of 3D TIs, such as Bi 2 Te 3 [7], Bi 2 Se 3 [8-10], and thallium-based compounds [11][12][13][14][15][16], were predicted and experimentally realized. Among the established 3D TIs, the binary tetradymite compounds, Bi 2 Se 3 and Bi 2 Te 3 have been mostly studied because of their rel- * Electronic address: kmiyamoto@hiroshima-u.ac.jp atively large energy gap and the simplest TSS.…”

“…A number of 3D TIs, such as Bi 2 Te 3 [7], Bi 2 Se 3 [8-10], and thallium-based compounds [11][12][13][14][15][16], were predicted and experimentally realized. Among the established 3D TIs, the binary tetradymite compounds, Bi 2 Se 3 and Bi 2 Te 3 have been mostly studied because of their rel- * Electronic address: kmiyamoto@hiroshima-u.ac.jp atively large energy gap and the simplest TSS.…”

Observation of a highly spin-polarized topological surface state in GeBi2Te4

“…5,6 A number of materials that hold spin-polarized TSSs have been intensively studied, such as Bi 1−x Sb x , 7,8 Bi 2 Se 3 , 9-12 Bi 2 Te 3 , 13,14 and thallium-and lead-based ternary compounds. [15][16][17][18][19][20][21][22][23] Among these materials, Bi 2 Se 3 has been regarded as the most promising three-dimensional (3D) TI because it possesses a single TSS in a rather wide bulk energy gap. 9,10 However, no surface-isolated conduction has been observed for this binary compound even with the low carrier density realized by the hole doping.…”

Temperature-Induced Topological Phase Transitions: Promoted versus Suppressed Nontrivial Topology

“…The crystal structure of BiTlS 2 and BiTlSe 2 is a closepacked stacking of hexagonal planes whose unit cell contains a single formula unit [41], as shown in Fig.1. We obtained the lattice parameters by minimizing the internal stress (< 10 −8 Ha/Bohr 3 ), giving a = 4.207Å and c = 22.492Å for BiTlS 2 , and a = 4.372Å and c = 23.058Å for BiTlSe 2 , which are slightly overestimated compared to experiments (a = 4.1Å, c = 21.9Å for BiTlS 2 , and a = 4.255Å, c = 22.307Å for BiTlSe 2 ) [3].…”