Work Package B: Task 3

Developing a theory for magnon-plasmon hybridization and application of that in ultrafast spin-current generation and spin pumping

Plasmonics, the study of plasmons, and magnonics, the study of magnons, have so far been developed independently. Notably, metallic magnetic materials support both charge and magnon transport. In 3D metallic systems, there is a large intrinsic bandgap of optical frequency in the plasmon dispersion; such systems cannot couple to coherent magnons, which typically have much less energy. In 2D metallic systems, however, the plasmon dispersion is gapless. Therefore, exciting plasmons with energies in the range of the coherent magnon frequencies, GHz in FMs and THz in AFMs, is possible via ultrafast laser pulses. Such magneto-plasmons are expected to be technologically important because they would enable the development of subwavelength-size devices and ultrafast spin dynamics in nanosystems.

We wish to investigate the possibility of ultrafast plasmonic generation of spin currents and the rate of change of the plasmon occupation. We consider a microscopic formulation of the magnon-plasmon interaction in metallic 2D magnetic systems. Using an effective Hamiltonian, we calculate the plasmon and magnon dispersion of a 2D magnetic system within the random phase approximation. Then, we examine the ultrafast spin-current generation by magnon-plasmon resonance.