Magnon-driven chiral charge and spin pumping and electron-magnon scattering from time-dependent quantum transport combined with classical atomistic spin dynamics*

In this study, we employ recently developed [M. D. Petrovic et. al., Phys. Rev. Appl. 10, 054038 2018] multiscale time-dependent-quantum transport/classical-micromagnetics formalism (TDNEGF-LLG) to simulate how spin-polarized steady-state current of electrons interacts with a magnon modelled as a classical spin wave. We investigate electronic spin and charge currents generated by the excitation of a single frequency spin wave in a one-dimensional finite-size magnetic nanowire composed of classical local magnetic moments precessing around the anisotropy axis while the phase of the precession of adjacent moments varies harmonically over the wavelength of spin wave with uniform precession cone angle. We show that spin wave hosted in the middle of two metallic leads pumps chiral electronic spin and charge currents into the leads, which can be flipped by reversing the direction of magnonic spin current. The mechanism behind our prediction is nonadiabaticity due to time-retardation effects, which makes the time-dependent non-equilibrium spin density misaligned with the adiabatic direction even without spin-orbit interaction, and in the absence of magnetic or spin-orbit impurities.