2D layered transport properties from topological insulator Bi$_2$Se$_3$ single crystals and micro flakes

TL;DR

This study investigates the layered transport properties of Bi$_2$Se$_3$ topological insulator crystals and flakes, revealing surface state dominance in semiconducting samples and layered metallic behavior in others through magnetotransport and spectroscopic analyses.

Contribution

It demonstrates the dominance of surface states in quantum corrections for semiconducting Bi$_2$Se$_3$ and highlights layered metallic contributions in high electron density samples.

Findings

Surface states dominate quantum corrections in semiconducting samples.

High electron density samples show layered metallic behavior.

Surface stability confirmed by photoelectron microscopy.

Abstract

Low-field magnetotransport measurements of topological insulators such as Bi$_2$Se$_3$ 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 ($\sim10^{19}$ 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 Bi$_2$Se$_3$ 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.