Toward Terahertz Spin-Orbitronics

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Abstract
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In future electronics, the charge of electrons as well as their spin and orbital angular momentum will serve as information carriers. This spin-orbitronic approach has led to fascinating functionalities that include the electric transport and detection of electron spin and the electric writing of magnetic information up to megahertz and gigahertz frequencies. However, to be competitive and compatible with electronics, spin orbitronic operations need to ultimately work at extremely high frequencies approaching the terahertz range (1 THz=1012 Hz). In this talk, I will first discuss how terahertz spin-orbitronic circuits can be realized by using ultrafast spin-orbitronic batteries, conductors and detectors. Our circuits are driven by femtosecond laser pulses (down to 10 fs) and interrogated by the electric-field transients (0.3-30 THz) they emit. This approach provides new insights into spin-orbital transport and spin-charge conversion in, e.g., magnetic and topological materials, all on the femtosecond scale of electronic relaxation processes. In a second, reciprocal scheme, we use ultrashort terahertz electric-field pulses to induce and reveal the first steps of spin-orbital accumulation, spin-orbit torques and spin-Hall magneto-resistance. By pushing the terahertz field to amplitudes of ~1 MV/cm, we can even write an antiferromagnetic bit, fully electrically and within picoseconds. Finally, we take advantage of spin-orbitronic effects to develop new sources and detectors of ultrabroadband terahertz radiation for photonic and sensing applications down to the nanoscale.

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About the Speaker
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Prof. Kampfrath graduated in 2006 on ultrafast charge dynamics in carbon nanotubes and graphite. As postdoc, he worked on near-field microscopy and ultrafast control of slow light in nanophotonic structures. In 2010, he became group leader at the FHI Max Planck Institute in Berlin (Germany) and, in 2017, full professor at the Freie Universität of Berlin (Germany). His research addresses ultrafast processes in quantum materials. A particular focus lies on the dynamics of charge, energy and angular momentum in nanostructures and at interfaces, with applications in spin-orbitronics and terahertz photonics. Awards include a Consolidator Grant (2015), Proof of Concept Grant (2023) and Advanced Grant (2024) of the European Research Council (ERC). He co-founded the start-up TeraSpinTec.