Electron spin controls terahertz plasmonic propagation

An electron-spin-dependent plasmonic-transport effect at terahertz frequencies has been demonstrated by a team of researchers from the University of Alberta (Edmonton, Canada) and the Naval Research Laboratory (Washington, D.C.). Spintronic structures consisting of subwavelength-size ferromagnetic particles coated with nonmagnetic nanolayers were excited with a single-cycle terahertz electric-field pulse; the incident electric field induced nonresonant plasmons on the surface of the individual ferromagnetic/nonmagnetic composite particles. Dipolar electric fields associated with the particle plasmons coupled between closely spaced particles via a “nearest-neighbor” interaction and coherently radiated into the far field at the edge of the sample. When a magnetic field was applied to the spintronic medium, changes in electron-spin-induced resistivity on the surface of the particles modulated the radiated electromagnetic field.

Remarkably, terahertz radiation that was propagated through the spintronic ferromagnetic/nonmagnetic structures showed a dramatically increased magnetically dependent attenuation relative to that of structures consisting of purely ferromagnetic or nonmagnetic particles. The demonstration of spin-dependent plasmonic propagation offers a new degree of freedom in the design of next-generation photonics devices. Furthermore, there is good evidence that this spin-dependent effect is nonvolatile, such that modulation can occur without the further application of power. Contact Abdulhakem Elezzabi at [email protected].