2D layered transport properties from topological insulator Bi2Se3 single crystals and micro flakes

Abstract

Low-field magnetotransport measurements of topological insulators such as Bi2Se3 are important for revealing the nature of topological surface states by quantum corrections to the conductivity, such as weak-antilocalization. Recently, a rich variety of high-field magnetotransport properties in the regime of high electron densities (∼1019 cm−3) were reported, which can be related to additional two-dimensional layered conductivity, hampering the identification of the topological surface states. Here, we report that quantum corrections to the electronic conduction are dominated by the surface states for a semiconducting case, which can be analyzed by the Hikami-Larkin-Nagaoka model for two coupled surfaces in the case of strong spin-orbit interaction. However, in the metallic-like case this analysis fails and additional two-dimensional contributions need to be accounted for. Shubnikov-de Haas oscillations and quantized Hall resistance prove as strong indications for the two-dimensional layered metallic behavior. Temperature-dependent magnetotransport properties of high-quality Bi2Se3 single crystalline exfoliated macro and micro flakes are combined with high resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy, confirming the structure and stoichiometry. Angle-resolved photoemission spectroscopy proves a single-Dirac-cone surface state and a well-defined bulk band gap in topological insulating state. Spatially resolved core-level photoelectron microscopy demonstrates the surface stability.

High-temperature quantum oscillations of the Hall resistance in bulk Bi2Se3

“…18 ). Different from that, for n ≥ 2 ⋅ 10 19 cm −3 a bulk quantum Hall effect (QHE) with 2D-like transport behavior was reported 3,16 . Its origin remains unidentified.…”

“…Most of the investigations of bulk Bi 2 Se 3 conclude that the Fermi surface is 3D 3,12,14,17,30 , usually from the angular dependence of the SdH oscillations. However, in the search of TSS and QHE some works evaluated the Fermi surface as 2D 15,16 .…”

“…For the charge carrier density, we estimate three different values for the core (from ref. 3 ), the shell (from the Hall measurements) and the topological surface (from the ARPES measurements): n core ≈ 1.2 ⋅ 10 17 cm −3 , n shell ≈ 2 ⋅ 10 19 cm −3 and n TSS = 1.2 ⋅ 10 13 cm −2 , respectively. In the semiconducting-like core region, the Fermi level (chemical potential) is in the gap close to the bottom of the conduction band, whereas in the metallic-like shell region the Fermi level is in the conduction band (see Supplementary Information Sec.…”

“…5). The semiconducting-like core was proven by the preparation of semiconducting micro flakes 3 . The metallic-like shell region due to Se depletion dominates the transport mechanism observed here as metallic and 2D layered effects.…”

“…Therefore, the transport properties of Bi 2 Se 3 are generally dominated by bulk conduction. In particular, the temperature dependence of the electrical resistivity ρ is metallic-like 3,14–17 and Shubnikov-de Haas (SdH) oscillations in the longitudinal resistivity ρ xx show the characteristic signatures for a 3D Fermi surface 14,17 . For highly Sb-doped samples with lower carrier density cm −3 , the TSS can be detected via additional SdH oscillations with a frequency B SdH higher than that of the bulk and the Hall resistivity ρ xy exhibits quantum oscillations for a carrier density n < 5 ⋅ 10 18 cm −3 (ref.…”