Magnon driven chiral charge and spin pumping and electron-magnon scattering from time-dependent-quantum-transport/classical-micromagnetics framework

Using newly developed time-dependent-quantum-transport/classical-micromagnetics framework, we investigate interaction between conduction electrons and a single spin wave (SW) coherently excited within a metallic ferromagnetic nanowire. The classical micromagnetics describes SW as a collection of localized magnetic moments whose vectors of fixed length precess with harmonic variation in the phase of precession of adjacent moments around the local magnetization direction. Conversely, electrons interacting with SW are described quantum-mechanically using time-dependent nonequilibrium Green functions. When the nanowire hosting SW is attached to two normal metal (NM) leads, even in the absence of any external dc bias voltage between them the SW pumps chiral electronic charge and spin currents into the leads---they scale linearly with the frequency of the precession and their direction is tied to the direction of wave propagation. This is in contrast to standard pumping of identical spin currents in both directions, and no charge current, by the uniform precession mode. Upon applying dc bias voltage to inject spin-polarized charge current from the left NM lead, electrons interact with SW where we quantify outflowing charge and spin current into the right NM lead due to both scattering off time-dependent potential generated by the SW and superposition with the currents pumped by the SW itself. Finally, we use Lorentzian voltage pulse to excite the so-called "leviton" out of the Fermi sea, which carries two electron charges with no accompanying electron-hole pairs. The scattering of such soliton-like quasiparticle from the SW results in the change of its width and the corresponding charge and spin it carries.