Laser-induced Terahertz Spin Current Nanoscopy

Objective

TeraSCN will establish spintronic terahertz emission nanoscopy (STEN), the first European tabletop platform capable of imaging spin current dynamics with nanometer spatial and femtosecond temporal resolution, the natural time and length scales of spintronic processes. This development is achieved by combining spintronic terahertz emission spectroscopy with scattering-type scanning near-field optical microscopy (s-SNOM). I will adapt and optimize a commercial s-SNOM for STEN operation and determine its instrument response function, enabling extraction of spin current dynamics from measured terahertz signals. Unlike synchrotron-based X-ray techniques (e.g., XMCD-PEEM), STEN provides superior spatiotemporal access at much lower cost and with year-round availability, ensuring broad adoption across European laboratories. With this capability, TeraSCN will address fundamental open questions in spintronics. I will resolve spin-current dynamics at domain walls, defects, and pinning sites to identify their transport mechanisms (ballistic, diffusive, tunneling). I will also image light-induced terahertz spin currents in magnetic skyrmions at previously inaccessible resolution, probing spin and magnon relaxation and experimentally testing the predicted skyrmion topological terahertz resonance. These experiments will deliver the first direct movies of spin-current dynamics at their natural scales. TeraSCN will have both scientific and technological impact. Scientifically, it will provide a powerful tool for uncovering fundamental spin physics. Technologically, by elucidating how defects and nanoscale textures govern spin-current efficiency, STEN will accelerate the development of next-generation spintronic technologies, including racetrack memories, spin-based logic, and neuromorphic devices.