Theme 3 colloquium: 'Coherent spin-wave transport in an antiferromagnet' (Lecture)

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. 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. The wavepacket features magnons with detected wavelengths down to 125 nm that propagate with supersonic velocities 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.

References

[1] V.V. Kruglyak et al. J. Phys. D 43 (2010) 264001
[2] B. Lenk et al., Phys. Rep. 507 (2011) 107
[3] A.V. Chumak et al. Nat. Phys. 11 (2015) 453
[4] T. Jungwirth et al. Nat. Nanotechnol. 11 (2016) 231

We are looking forward to seeing you!