4.8 Article

Terahertz Spin-to-Charge Conversion by Interfacial Skew Scattering in Metallic Bilayers

Journal

ADVANCED MATERIALS
Volume 33, Issue 9, Pages -

Publisher

WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202006281

Keywords

interface; skew scattering; spin-to-charge conversion; terahertz emission spectroscopy

Funding

  1. collaborative research center [SFB TRR 227, SFB TRR 173, 268565370]
  2. ERC H2020 through projects CoG TERAMAG/Grant [681917]
  3. ERC-2019-SyG 3D MAGiC/Grant [856538]
  4. MSCA ITN MagnEfi/Grant [860060]
  5. FET projects SKYTOP/Grant [824123]
  6. s-NEBULA/Grant [863155]
  7. Projekt DEAL

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This study investigated ultrafast spin-to-charge-current conversion in F|N bilayers using terahertz emission spectroscopy. It found that varying the structure of the F/N interface can significantly impact the amplitude and polarity of the charge current, with a dominant interface contribution observed in materials with small spin Hall angle. The results suggest the potential of skew scattering for enhancing interfacial spin-to-charge conversion.
The efficient conversion of spin to charge transport and vice versa is of major relevance for the detection and generation of spin currents in spin-based electronics. Interfaces of heterostructures are known to have a marked impact on this process. Here, terahertz (THz) emission spectroscopy is used to study ultrafast spin-to-charge-current conversion (S2C) in about 50 prototypical F|N bilayers consisting of a ferromagnetic layer F (e.g., Ni81Fe19, Co, or Fe) and a nonmagnetic layer N with strong (Pt) or weak (Cu and Al) spin-orbit coupling. Varying the structure of the F/N interface leads to a drastic change in the amplitude and even inversion of the polarity of the THz charge current. Remarkably, when N is a material with small spin Hall angle, a dominant interface contribution to the ultrafast charge current is found. Its magnitude amounts to as much as about 20% of that found in the F|Pt reference sample. Symmetry arguments and first-principles calculations strongly suggest that the interfacial S2C arises from skew scattering of spin-polarized electrons at interface imperfections. The results highlight the potential of skew scattering for interfacial S2C and propose a promising route to enhanced S2C by tailored interfaces at all frequencies from DC to terahertz.

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