Injection of orbital angular momentum into transition metals from first-principles
TLDR
This paper shows orbital currents in transition metals decay rapidly and convert to spin currents, challenging current experimental interpretations.
Key contributions
- Used quantum mechanical scattering calculations to study spin and orbital currents.
- Found injected orbital currents decay within a few atomic layers in transition metals.
- This rapid decay contradicts current experimental interpretations of orbital current length scales.
- Spin-orbit coupling converts injected orbital current into a spin current within a few atomic layers.
Why it matters
This research provides a new first-principles understanding of orbital current decay in transition metals. It challenges existing experimental interpretations and offers a fresh perspective on the physics behind the orbital Hall effect, crucial for spintronics.
Original Abstract
We use quantum mechanical scattering calculations implemented in a basis of tight-binding muffin-tin orbitals to calculate nonequilibrium spin and orbital currents in transition metals with a view to understanding the length scale on which they decay. In the case of spin currents, the relaxation length, called the spin-flip diffusion length, is reasonably well understood. We apply our experience with spin currents to study orbitally-polarized currents and find that they behave qualitatively differently. Upon injection from a lead, orbital currents decay within a few atomic layers contradicting the current interpretation of experimental results which appear to show exponential decay on the length scale of the spin-flip diffusion length and longer. When spin-orbit coupling is included, the injected orbital current is partially converted into a spin current within a few atomic layers. This insight provides a new perspective on the physics of the orbital Hall effect.
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