Coherent spin-wave transport in an antiferromagnet

TL;DR

This paper demonstrates the generation and detection of coherent, short-wavelength THz spin waves in an antiferromagnet, enabling ultrafast magnonic information transfer with potential for low dissipation and high speed.

Contribution

It reports the first efficient emission and detection of nanometer-scale coherent propagating magnons in an antiferromagnet using ultrashort light pulses.

Findings

Magnons with wavelengths down to 125 nm detected.

Magnons propagate at velocities up to 13 km/s.

Coherent spin waves are generated and observed at THz frequencies.

Abstract

Magnonics is a research field complementary to spintronics, in which the quanta of spin waves (magnons) replace electrons as information carriers, promising less energy dissipation. 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. Antiferromagnets can host spin waves at THz frequencies and are therefore seen as a future platform for the fastest and the least dissipative transfer of information. However, the generation of short-wavelength coherent propagating magnons in antiferromagnets has so far remained elusive. Here 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 nanoscale confinement of the laser field due to large absorption creates a strongly non-uniform spin excitation profile, thereby enabling the propagation of a broadband continuum of coherent THz spin waves. The wavepacket features magnons with detected wavelengths down to 125 nm and supersonic velocities up to 13 km/s that propagate over macroscopic distances. The long-sought source of coherent short-wavelength spin carriers demonstrated here opens up new prospects for THz antiferromagnetic magnonics and coherence mediated logic devices at THz frequencies.