Synthesis, Crystal and Topological Electronic Structures of New Bismuth Tellurohalides Bi₂TeBr and Bi₃TeBr

Abstract

Halogen substitution, i. e. bromine for iodine, in the series of topological Bi n TeI (n = 1, 2, 3) materials is conducted in order to explore an impact of anion exchange on the topological electronic structure. In the proof-of-concept study we demonstrate the applicability of the modular view on the crystal and electronic structures of the new Bi 2 TeBr and Bi 3 TeBr compounds. Along with the isostructural telluroiodides, they constitute a family of layered structures that are stacked from two basic building modules, [ ஶ ଶ Bi 2 ] and [ ஶ ଶ BiTeX] (X = I, Br). We present solid-state synthesis, thermochemical studies, crystal growth and crystal-structure elucidation of Bi 2 TeBr (sp.gr. R3 തm (no. 166), a = 433.04(2) pm, c = 5081.6(3) pm) and Bi 3 TeBr (sp.gr. R3m (no. 160), a = 437.68(3) pm, c = 3122.9(3) pm). First-principles calculations establish the topological nature of Bi 2 TeBr and Bi 3 TeBr. General aspects of chemical bonding appear to be similar for Bi n TeX (X = I, Br) with the same n, so that the alternation of the global gap size upon substitution is insignificant. The complex topological inversion proceeds between the states of two distinct modules, [ ஶ ଶ Bi 2 ] and [ ஶ ଶ BiTeBr]; thus, the title compounds can be seen as heterostructures built via a modular principle. Furthermore, highly disordered as well as incommensurately modulated ternary phase(s) are documented near the Bi 2 TeBr composition. Single-crystal X-ray diffraction experiments on BiTeBr and Bi 2 TeI resolve some discrepancies in the prior published work.

Dual topology in jacutingaite Pt2HgSe3

“…In a given material, details of the bulk bandstructure and of the surface potential will dictate if all or some of these four Dirac cones are observed. For instance, DFT calculations in Bi 2 TeI [41] have highlighted Dirac cones both atΓ and away from the TRIM, and similar results are found in Bi 2 TeBr [43] and in BiTe [44]. Different to these materials, Jacutingaite has two observable surface Dirac cones atX (see Fig.…”

“…Having established that Pt 2 HgSe 3 and Pd 2 HgSe 3 simultaneously realize weak and topological crystalline phases, we will now introduce tight-binding models that capture the essential topological features of this class of materials, which has been found to also include Bi 2 TeI [41,42], Bi 2 TeBr [43], BiTe [44] and BiSe [17]. Specifically, we will construct systems with three-fold rotation symmetry, which are both WTI and TCI [65].…”

“…In this work, we first address this issue and show that Pt 2 HgSe 3 is both a weak topological phase and a mirror-protected topological crystalline phase. This result places Jacutingaite in the list of materials which can host surface states protected by different, unrelated crystalline symmetries [17,[41][42][43][44][45]. Second, we construct minimal tight-binding models that capture the essential topological properties of this dual topological phase in materials with three-fold rotation symmetry and compare their associated surface spectral density with those of different materials in the class.…”

Transport properties of topologically non-trivial bismuth tellurobromides BinTeBr

“…2,[4][5][6][7] Although bismuth tellurides have been extensively studied and the investigation of mixed group 15 tellurides have potential for chemical modification, extending the idea of chemical diversification further leads to another class of layered bismuth compounds, Bi n TeX with n = 1-3 and X = Br, I. [8][9][10] The bismuth tellurohalides BiTeBr and BiTeI were first reported by Dönges in 1951. 11 Kulbachinskii et al 12 investigated the transport properties of BiTeBr and BiTeI singlecrystals, as well as the influence of BiI 3 and CuI doping in polycrystalline BiTeI specimens.…”

“…14 The first compound with increased bismuth content in this material system is Bi 2 TeI. 8 Subsequently, the bismuth-rich Bi 3 TeI and bromine analogs Bi 2 TeBr and Bi 3 TeBr were synthesized after tribochemical activation of the starting materials by Zeugner et al 9,10 All these compounds are structurally closely related to BiTeX and display the characteristic polar Te-Bi-X triple layer (A) separated by additional bismuth bilayers (B) in the van der Waals gap. Alternate stacking of these two building modules results in either the Bi 2 TeX (AAB) or Bi 3 TeX (AB) structure types (Fig.…”