Doping-controlled surface conduction in topological insulators with warping effects

TL;DR

This paper investigates how magnetic and nonmagnetic doping, along with warping effects, influence the surface electronic states and conductivity of topological insulators, revealing controllable surface conduction properties.

Contribution

It introduces a self-consistent $t$-matrix approach to analyze the impact of warping and doping on topological insulator surface states and conductivity, highlighting new control mechanisms.

Findings

Warpage suppresses high-energy surface density of states.

Nonmagnetic impurities break electron-hole symmetry at low warping.

Surface conductivity can be tuned by doping and magnetic field orientation.

Abstract

Based on a self-consistent $t$-matrix approximation, we explore the influence of magnetic and nonmagnetic doping on the surface electronic states and conductivity of topological insulators. We show that warping parameter has a crucial impact on the density of states and dc conductivity of the doped surfaces. As the warping strength is increased, the surface density of states at high energies is suppressed and the resonant states induced by impurities in the vicinity of the Dirac point gradually disappear. It is found that nonmagnetic impurities break electron-hole symmetry at low warping strength, while the symmetry remains unchanged when the surface is magnetically doped. Our findings reveal that surface conductivity can be controlled by tuning the doping, the direction of external magnetic field and that of impurity magnetic moments. Also, the surface conductivity features in topological insulators with warped energy dispersions are not significantly affected by the presence of impurities compared to that of materials with circular energy contour.