Phonon and Magnon Jets above the Critical Current in Nanowires with Planar Domain Walls.

We show through nonequilibrium nonadiabatic electron-spin-lattice simulations that above a critical current in magnetic atomic wires with a narrow domain wall (DW), a couple of atomic spaces in width, the electron flow triggers violent stimulated emission of phonons and magnons with an almost complete conversion of the incident electron momentum flux into a phonon and magnon flux. Just below the critical levels of the current flow, the DW achieves maximal velocity of about 3×10^{4}  m/s, entering a strongly nonadiabatic regime of DW propagation, followed by a breakdown at higher biases. Above this threshold, a further increase of the current with the applied bias is impossible-the electronic current suffers a heavy suppression and the DW stops. This poses a fundamental limit to the current densities attainable in atomic wires. At the same time it opens up an exciting way of generating the alternative quasiparticle currents, described above, once the requisite electronic-structure properties are met.