Proximity effects in topological insulators

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Motivated by the recent experimental progress and surge of interest in the electrical transport detection of the spin-orbit induced spin-momentum locking, we propose to perform systematic and comprehensive first-principles calculations of the proximity effects in 3d topological insulators, focusing on the Bi2Se3 family, but also on some novel structures. In particular, we plan to establish modifications to the Dirac band structures and extract relevant proximity exchange and spin-orbit couplings emergent in the surface states of the investigated materials. We will use common ferromagnets and tunnel barriers to model junctions with topological insulators, and evaluate the proximity effects caused by different junction materials compositions and tunnel barrier thicknesses. We also expect strong magnetoanisotropies of the proximity effects. To supplement the first-principles calculations, we will build realistic minimal phenomenological models, based on symmetry arguments, to fit and describe the proximity band structures, enabling large-scale numerical model magneto-transport charge and spin calculations for topological insulators with proximity regions due to ferromagnetic electrodes. Both the first-principles and model simulations will provide qualitative insights and quantitative information important for surface states spin and charge transport. We also expect that our work will clarify some pressing unresolved issues important for the interpretation of recent experiments as well as motivate and guide new experiments by predicting optimal materials and structural parameters for spin injection and detection, and spin-transfer torque phenomena.