Atom-specific spin mapping and buried topological states in a homologous series of topological insulators

Abstract

A topological insulator is a state of quantum matter that, while being an insulator in the bulk, hosts topologically protected electronic states at the surface. These states open the opportunity to realize a number of new applications in spintronics and quantum computing. To take advantage of their peculiar properties, topological insulators should be tuned in such a way that ideal and isolated Dirac cones are located within the topological transport regime without any scattering channels. Here we report ab-initio calculations, spin-resolved photoemission and scanning tunnelling microscopy experiments that demonstrate that the conducting states can effectively tuned within the concept of a homologous series that is formed by the binary chalcogenides (Bi 2 Te 3 , Bi 2 se 3 and sb 2 Te 3 ), with the addition of a third element of the group IV.

Electronic and spin structure of the topological insulator Bi2Te2.4Se0.6

“…Some of these compounds possess extraordinary wide fundamental energy gaps and nearly ideal Dirac cones [8,15]. It was also shown that the modification of such features of the electronic structure as the position of the Dirac point relative to the Fermi level and to the bulk valence band edge, the absence of bulk conduction band states at the Fermi level, etc., can be efficiently controlled by means of a variation of the third component concentration [1,[5][6][7]9,20] or by diluted metal atom doping [7].…”

“…Recently, it was demonstrated that ternary compounds based on binary TIs show a rich variety of TSSs [3,8,9,[14][15][16][17] including buried TSSs [3,8] and occupied and unoccupied TSSs in local energy gaps [8,18,19]. Some of these compounds possess extraordinary wide fundamental energy gaps and nearly ideal Dirac cones [8,15].…”

“…Topological insulators (TIs) are characterized by an insulating energy gap in the bulk and the gapless spin-polarized metallic surface states with linear Dirac-cone-like dispersion in the energy-momentum space with spin of electron locked perpendicular to its momentum (see, for instance, Refs. [1][2][3][4][5][6][7][8][9]). Owing to the opposite spin orientation for opposite sign of momentum, the topological surface states (TSSs) are protected from backscattering resulting in spin currents with reduced dissipation.…”

Bulk and surface electron dynamics in ap-type topological insulatorSnSb2Te4

“…These studies showed that the electron dynamics of TSSs is dominated by the bulk conduction band, but did not provide scattering rates between TSS and the conduction or valence band. Such information could be related to results obtained from transport measurements and would be important for device applications.Complex ternary Sb 2 Te 3 -based alloys possess a layer structure with a van der Waals gap between Te layers and were recently proposed to exhibit a topological surface state [9][10][11]. However, intrinsic p doping of antimony-containing materials does not permit to access the Dirac point by conventional angle-resolved photoelectron spectroscopy [12] even after doping by alkali-metal atoms [13].…”

Breaking time-reversal symmetry at the topological insulator surface by metal-organic coordination networks

“…Three-dimensional topological insulators (TIs), a novel class of materials in which an insulating bulk necessarily coexists with a metallic surface, have been attracting a great deal of attention for several years [1][2][3][4]. As a consequence of the strong spin-orbit coupling, the band gap in TIs gets inverted giving rise to a special type of surface states that have linear dispersion characteristic of Dirac fermions.…”