Electronic structure and x-ray magnetic circular dichroism in Mn-doped topological insulators Bi2Se3 and Bi2Te3

Abstract

We studied the structural, electronic, and magnetic properties of Mn-doped topological insulators ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ and ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ within the density-functional theory (DFT) using the generalized gradient approximation (GGA) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. The x-ray absorption spectra (XAS) and x-ray magnetic circular dichroism at the Mn $K$ and ${L}_{2,3}$ edges were investigated theoretically from first principles. The calculated results are in good agreement with experimental data. The complex fine structure of the Mn ${L}_{2,3}$ XAS in Mn-doped ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ and ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ was found to be not compatible with a pure ${\mathrm{Mn}}^{3+}$ valency state. Its interpretation demands mixed valent states. The theoretically calculated x-ray emission spectra at the Mn $K$ and ${L}_{2,3}$ edges are also presented and analyzed.