Sudden gap closure across the topological phase transition inBi2−xInxSe3

Abstract

The phase transition from a topological insulator to a trivial band insulator is studied by angleresoled photoemission spectroscopy on Bi2−xInxSe3 single crystals. We first report the complete evolution of the bulk band structures throughout the transition. The robust surface state and the bulk gap size (∼ 0.50 eV) show no significant change upon doping for x = 0.05, 0.10 and 0.175. At x ≥ 0.225, the surface state completely disappears and the bulk gap size increases, suggesting a sudden gap-closure and topological phase transition around x ∼ 0.175−0.225. We discuss the underlying mechanism of the phase transition, proposing that it is governed by the combined effect of spin-orbit coupling and interactions upon band hybridization. Our study provides a new venue to investigate the mechanism of the topological phase transition induced by non-magnetic impurities.

Anomalous behavior of the electronic structure of ( Bi1−xInx)2Se3 across the quantum phase transition from topological to tri

“…This behavior appears in contrast to the scenario of a sudden closure of an otherwise constant bulk band gap as proposed in Ref. 21. Conversely, our findings taken altogether clearly indicate that the gap closing is instead gradual and continuous.…”

Dimensional Crossover and Topological Nature of the Thin Films of a Three-Dimensional Topological Insulator by Band Gap Engineering

“…In this case, the (Bi1-xInx)2Se3 film will open a surface state gap regardless of the thickness, which is exactly what happens in previous works. [21][22][23][24] At xB, the transition from 2D GSS to NI happens, independent of the number of layers. We note here that, because of the quantum well states in thin (Bi1-xInx)2Se3 films, the negative bulk gap may not close at the bulk critical point.…”

“…For example, BiTlSe2 bulk crystal doped with S, BiTl(S1-xSex)2, is the first system where TPT was observed. 20,21 TPT from topological-metallic to normal-insulating states has further been realized in (Bi1-xInx)2Se3 19,[22][23][24] and (Bi1-xSbx)2Se3 25 single crystals and films. To date, the experimental exploration of TPT has been mainly limited on thick films and bulk samples, [20][21][22][24][25][26] whereas only few thickness-depended transport measurements have focused on ultrathin (Bi1-xInx)2Se3 films down to 2 QLs.…”

“…20,21 TPT from topological-metallic to normal-insulating states has further been realized in (Bi1-xInx)2Se3 19,[22][23][24] and (Bi1-xSbx)2Se3 25 single crystals and films. To date, the experimental exploration of TPT has been mainly limited on thick films and bulk samples, [20][21][22][24][25][26] whereas only few thickness-depended transport measurements have focused on ultrathin (Bi1-xInx)2Se3 films down to 2 QLs. 19,23 For ultrathin (Bi1-xInx)2Se3 samples, with increasing In substitution, the spin-orbit coupling (SOC) strength decreases and drives the system from a topologically nontrivial state to a trivial state, accompanied by the inverted bulk gap closure and reopening.…”

Electronic Structure of the Metastable Epitaxial Rock-Salt SnSe {111} Topological Crystalline Insulator

“…The measured bands of Sn-terminated SnSe f111g are accurately reproduced by our first-principles calculations. Despite the fact that most topological material design focuses on composition [28,29], this work paves the way for obtaining a tunable Dirac point and Fermi velocity in TCI by modifying the surface termination; it also clearly shows one potential approach to manipulation of topologically nontrivial surface states by tuning the surface structure through the choice of growth conditions or decapping conditions.…”