Dmytro Afanasiev
Magnonics is a research field complementary to spintronics, in which quanta of spin waves (magnons) replace electrons as information carriers, promising lower dissipation [1,2]. The development of ultrafast nanoscale magnonic logic circuits calls for new tools and materials to generate coherent spin waves with frequencies as high, and wavelengths as short, as possible [3]. Antiferromagnets can host spin waves at terahertz (THz) frequencies and are therefore seen as a future platform for the fastest and the least dissipative transfer of information [4]. However, the generation of short-wavelength coherent propagating magnons in antiferromagnets has so far remained elusive. We report the efficient emission and detection of a nanometer-scale wavepacket of coherent propagating magnons in antiferromagnetic DyFeO3 using ultrashort pulses of light [5]. The subwavelength confinement of the laser field due to large absorption creates a strongly non-uniform spin excitation profile, enabling the propagation of a broadband continuum of coherent THz spin waves (see Fig. 1). The wavepacket features magnons with detected wavelengths down to 125 nm that propagate with supersonic velocities V0 of more than 13 km/s into the material. This long-sought source of coherent short-wavelength spin carriers opens up new prospects for THz antiferromagnetic magnonics and nanoscale coherence-mediated logic devices at THz frequencies.
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[3] A.V. Chumak et al. Nat. Phys. 11, 453 (2015)
[4] T. Jungwirth et al. Nat. Nano. 11, 231 (2016)
[5] J.R. Hortensius et al. Nat. Phys. 17, 1001 (2021)