We investigate the injection of quasiparticle spin currents into a superconductor via spin pumping from an adjacent FM layer.To this end, we use NbN/\ch{Ni80Fe20}(Py)-heterostructures with a Pt spin sink layer and excite ferromagnetic resonance in the Py-layer by placing the samples onto a coplanar waveguide (CPW). A phase sensitive detection of the microwave transmission signal is used to quantitatively extract the inductive coupling strength between sample and CPW, interpreted in terms of inverse current-induced torques, in our heterostructures as a function of temperature. Below the superconducting transition temperature Tc, we observe a suppression of the damping-like torque generated in the Pt layer by the inverse spin Hall effect (iSHE), which can be understood by the changes in spin current transport in the superconducting NbN-layer. Moreover, below Tc we find a large field-like current-induced torque.
@article{arxiv.2007.15569,
title = {Temperature-dependent spin-transport and current-induced torques in superconductor/ferromagnet heterostructures},
author = {Manuel Müller and Lukas Liensberger and Luis Flacke and Hans Huebl and Akashdeep Kamra and Wolfgang Belzig and Rudolf Gross and Mathias Weiler and Matthias Althammer},
journal= {arXiv preprint arXiv:2007.15569},
year = {2021}
}