Terahertz spin-to-charge conversion by interfacial skew scattering in magnetic metal bilayers

An efficient spin-to-charge current conversion (S2C) is important for the detection and generation of spin currents in spin-based electronics [1]. Interfaces of heterostructures are known to have a marked impact on this process [2]. Here, we study ultrafast S2C at interfaces by terahertz (THz) emission spectroscopy [3-4] in a model system: F|N bilayers consisting of thin metal films of a ferromagnetic layer F and nonmagnetic layer N with strong and weak spin-orbit coupling (SOC). Varying the interface composition allows us to drastically change the amplitude and even invert the polarity of the THz charge current that is induced by S2C close to the interface. Remarkably, when N is a material with weak SOC, we find a dominant interface contribution to the ultrafast S2C. Symmetry arguments and first-principles calculations strongly suggest that the interfacial S2C arises from skew scattering of spin-polarized electrons at interface imperfections. Our results paves the towards designing S2C by interfacial skew scattering.

References
[1] F. Hellman et al., Rev. Mod. Phys. 89,025006 (2017)
[2] M.B. Jungfleisch et al., Phys. Rev. Lett. 121, 086801 (2018)
[3] T. Kampfrath et al., Nature Nanotech. 8, 256 (2013)
[4] T. Seifert et al., Nature Phot. 10, 483 (2016)