Ferromagnetism and topological surface states of manganese doped Bi ₂Te₃: Insights from density-functional calculations

Based on first-principles calculations, the electronic, magnetic, and topological characters of manganese (Mn) doped topological insulator Bi ₂Te₃ were investigated. The Mn substitutionally doped Bi₂Te₃, where Mn atoms tend to be uniformly distributed, was shown to be p-type ferromagnetic, arising from hole-mediated Ruderman-Kittel-Kasuya-Yosida interaction. Mn doping leads to an intrinsic band splitting at Γ point, which is substantially different from that of nonmagnetic dopant. The topological surface state of Bi₂Te ₃ is indeed gapped by Mn doping; however, the bulk conductance limits the appearance of an insulating state. Moreover, the n-type doping behavior of Bi₂Te₃ is derived from Mn entering into the van der Waals gap of Bi₂Te₃.