A computational method to estimate spin-orbital interaction strength in solid state systems

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A computational method to estimate spin-orbital interaction strength in solid state systems

Authors

Qiangqiang Gu, Shishir Kumar Pandey

Abstract

Spin-orbit coupling (SOC) drives interesting and non-trivial phenomena in solid state physics, ranging from topological to magnetic to transport properties. Thorough study of such phenomena often require effective models where SOC term is explicitly included. However, estimation of SOC strength for such models mostly depend on the spectroscopy experiments which can only provide a rough estimate. In this work, we provide a simple yet effective computational approach to estimate the on-site SOC strength using a combination of the $ab$ $initio$ and tight-binding calculations. We demonstrate the wider applicability and high sensitivity of our method considering materials with varying SOC strengths and the number of SOC active ions. The estimated SOC strengths agree well with the proposed values in literature lending support to our methodology. This simplistic approach can readily be applied to a wide range of materials.

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3 comments

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Dr.  Pandey -- Thanks for your contribution. Quick question: DFT is known to underestimate bandages of semiconductors (eV scales). How can it be sensitive to spin-orbital effects, which are typically orders of magnitude smaller?
Thanks,
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skpandey

Thanks for your question, though I could not understand what is the meaning of DFT being sensitive to SOC effects. As far as I know, the inaccuracy of band gaps in semiconductors is related to exchange-correlation part of the potential which fail to correctly describe the conduction bands. However, the valence bands near the Fermi level, which is of importance when observing the effects of SOC, are quite accurately describe within DFT. So, however small changes be, DFT can in-principle should be able to capture it. I may not be very convincing with my answer, but sorry I don't have a better one for you. 

Shishir 

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skpandey

Sorry, forgot to mention it correctly " However, the valence bands near the Fermi level, which is of importance when observing the effects of SOC, are quite accurately describe within DFT except the contribution from the self-interaction term". 

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