Electronic structure and x-ray magnetic circular dichroism in Mn-doped topological insulatorsBi2Se3andBi2Te3

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.