Edge and interfacial states in a two-dimensional topological insulator: Bi(111) bilayer onBi2Te2Se

Abstract

The electronic states of a single Bi(111) bilayer and its edges, suggested as a two dimensional topological insulator, are investigated by scanning tunneling spectroscopy (STS) and first-principles calculations. Well-ordered bilayer films and islands with zigzag edges are grown epitaxially on a cleaved Bi2Te2Se crystal. The calculation shows that the band gap of the Bi bilayer closes with a formation of a new but small hybridization gap due to the strong interaction between Bi and Bi2Te2Se. Nevertheless, the topological nature of the Bi bilayer and the topological edge state are preserved only with an energy shift. The edge-enhanced local density of states are identified and visualized clearly by STS in good agreement with the calculation. This can be the sign of the topological edge state, which corresponds to the quantum spin Hall state. The interfacial state between Bi and Bi2Te2Se is also identified inside the band gap region. This state also exhibits the edge modulation, which was previously interpreted as the evidence of the topological edge state [F. Yang et al., Phys. Rev. Lett. 109, 016801 (2012)].

Electronic states of SnTe and PbTe (001) monolayers with supports

“…However, there are reports that bilayer Bi films are grown on Bi 2 Te 3 [16], Bi 2 Te 2 Se [17], and Bi 2 Se 3 [18] substrates in a pseudomorphic structure. The lattice mismatch of bulk lattices in the last case is about 10%.…”

Colloquium: Topological band theory

“…(Wada et al 2011;Chuang et al 2013) Some of these thin films have been synthesized in various experiments but there still is no transport evidence for their being QSH insulators. Chun-Lei et al 2013;Kim, Jin, et al 2014) A number of strategies for engineering topological states in 2D systems or their heterostructures have been proposed. Examples are: (i) Adding adatoms of heavy elements in the graphene structure to induce a stronger SOC for driving a topological phase transition (Weeks et al 2011;Kane and Mele 2005a); (ii) Applying circularly polarized laser field on a 2D electronic system where the light field acts like a Rashba-type SOC to generate a non-trivial gap in an optical lattice (Inoue and Tanaka 2010); (iii) Stacking two Rashba-type spin-orbit coupled 2D electron gases with opposite signs of Rashba coupling in adjacent layers in heterostructure geometry (Das and Balatsky 2013); and, (iv) GaAs/Ge/GaAs heterostructure with opposite semiconductor interfaces acting as Rashba-bilayers to allow a band inversion yielding a 15 meV or larger insulating gap.…”

Atomic and electronic structure of bismuth-bilayer-terminatedBi2Se3(0001) prepared by atomic hydrogen etching

“…They are now regarded as a prototype of an elemental 2D TI [10,11]. Recent studies have aimed to prepare bismuth BLs by using different methods such as molecular beam epitaxy [12][13][14][15], exfoliation [16], or by investigating step edges of a Bi(111) surface [17].…”