Design of Magnetic Interactions in Doped Topological Insulators

Magnetic impurities and their long-range interaction (ferromagnetic)order play pivotal roles in the topological phase transition from QSHIto QAHI. This transition transforms helical edge states belonging to theQSHI for 2D TIs (surface states for 3D TI) to the chiral edge states inQAHI for 2D TIs (surface states for 3D TI). Due to such chiral states, theQAHIs forbid back-scattering in electron conducting channels, which inturn provide passionless current and increase energy efficiency for conduct-ing channels. The chiral states are consist of single spin electrons whichprovide spin currents from conventional charge currents. Regarding theproperties of QAHIs, the QAHIs opens a new venue for low-energy elec-tronics, spintronics and quantum computation. Independently, the V-and Cr-doped as well as their co-doping (Sb, Bi)2 Te3 showsstable QAHE but with very low temperatures (≤ 0.5K). In this highthroughput ab-initio work, we will investigate other possible co-doping,dimer calculations, from the d-block elements in 3D TI Bi2 Te3 . For thispurpose, we have extended AiiDA-KKR plugins by developing combine-impurity workflow called combine imps wc using GF formulation of DFTcode (KKR-GF method) and the new workflow is capable to run multi-impurity calculations. Here, the dimer calculations are in the main fo-cus, and from the calculation results we will analyze Heisenberg isotropiccollinear interaction (Jij ), Dzyaloshinskii–Moriya interaction (DMI, Dij ),and their ratio for each possible impurity couple. Finally, using the ob-tained Jij data we have implemented some linear regression machine learn-ing tools to understand better the dependency of Jij on some well-knownfactors e.g. inter-impurity distance, electronegativity. Our results fromthe notion of this work will give a list of some potential impurities andafter their potential impurity combinations for stable QAHE. It will alsorender an impression of implementation of machine learning approach fordesigning better magnetic interactions in TIs.