OptimizingBi2−xSbxTe3−ySeysolid solutions to approach the intrinsic topological insulator regime

Abstract

To optimize the bulk-insulating behavior in the topological insulator materials having a tetradymite structure, we have synthesized and have characterized single-crystal samples of ${\mathrm{Bi}}_{2\text{\ensuremath{-}}x}{\mathrm{Sb}}_{x}{\mathrm{Te}}_{3\text{\ensuremath{-}}y}{\mathrm{Se}}_{y}$ solid solution at various compositions. We have elucidated that there are a series of intrinsic compositions where the acceptors and donors compensate each other and present a maximal bulk-insulating behavior. At such compositions, the resistivity can become as large as several $\ensuremath{\Omega}$ cm at low temperatures, and one can infer the role of the surface-transport channel in the nonlinear Hall effect. In particular, the composition of ${\mathrm{Bi}}_{1.5}{\mathrm{Sb}}_{0.5}{\mathrm{Te}}_{1.7}{\mathrm{Se}}_{1.3}$ achieves the lowest bulk carrier density and appears to be best suited for surface-transport studies.