Simultaneous Magnetic and Charge Doping of Topological Insulators with Carbon

TL;DR

This study demonstrates that carbon doping in Bi2Se3 can simultaneously induce magnetism and hole doping, opening a sizable surface Dirac gap while maintaining the Fermi level within the bulk gap, simplifying the realization of insulating topological surface states.

Contribution

First-principles calculations show that a single carbon dopant can induce both magnetic and charge doping in Bi2Se3, creating insulating massive surface states.

Findings

Carbon substitution opens a Dirac gap of 53-85 meV.

Fermi level remains inside the bulk gap near the Dirac point.

Carbon doping induces spontaneous spin polarization and magnetic moments.

Abstract

A two-step doping process, magnetic followed by charge or vice versa, is required to produce insulating massive surface states in topological insulators for many physics and device applications. Using first-principles calculations, we demonstrate here simultaneous magnetic and hole doping achieved with a single dopant, carbon, in Bi2Se3. Carbon substitution for Se (CSe) results in an opening of a sizable surface Dirac gap (53-85 meV), while the Fermi level (EF) remains inside the bulk gap and close to the Dirac point at moderate doping concentrations. The strong localization of 2p states of CSe favors spontaneous spin polarization via a p-p interaction and formation of ordered magnetic moments mediated by the surface state. Meanwhile, holes are introduced into the system by CSe. This dual function of carbon doping suggests a simple way to realize insulating massive topological surface states.