Tailoring Magnetic Doping in the Topological Insulator Bi2Se3

TL;DR

This study uses first-principles calculations to explore how magnetic doping with transition metals like Cr and Fe can induce ferromagnetism in Bi2Se3, a topological insulator, potentially enabling magnetic control of its electronic properties.

Contribution

It provides a detailed theoretical analysis of the energetics, electronic structure, and magnetic interactions of transition metal dopants in Bi2Se3, highlighting conditions for ferromagnetism and insulating behavior.

Findings

Cr doping can induce ferromagnetism while maintaining insulating properties.

Fe doping tends to produce weak antiferromagnetic interactions.

Dopant site preference favors substitutional over interstitial positions.

Abstract

We theoretically investigate the possibility of establishing ferromagnetism in the topological insulator Bi2Se3 via magnetic doping of 3d transition metal elements. The formation energies, charge states, band structures, and magnetic properties of doped Bi2Se3 are studied using first-principles calculations within density functional theory. Our results show that Bi substitutional sites are energetically more favorable than interstitial sites for single impurities. Detailed electronic structure analysis reveals that Cr and Fe doped materials are still insulating in the bulk but the intrinsic band gap of Bi2Se3 is substantially reduced due to the strong hybridization between the d states of the dopants and the p states of the neighboring Se atoms. The calculated magnetic coupling suggests that Cr doped Bi2Se3 is possible to be both ferromagnetic and insulating, while Fe doped Bi2Se3 tends to be weakly antiferromagnetic.