Protected Long-Distance Guiding of Hypersound Underneath a Nanocorrugated Surface

On-chip phonon-magnon reservoir for neuromorphic computing

Reservoir computing is a concept involving mapping signals onto a high-dimensional phase space of a dynamical system called "reservoir" for subsequent recognition by an artificial neural network. We implement this concept in a nanodevice consisting of a sandwich of a semiconductor phonon waveguide and a patterned ferromagnetic layer. A pulsed write-laser encodes input signals into propagating phonon wavepackets, interacting with ferromagnetic magnons. The second laser reads the output signal reflecting a phase-sensitive mix of phonon and magnon modes, whose content is highly sensitive to the write- and read-laser positions. The reservoir efficiently separates the visual shapes drawn by the write-laser beam on the nanodevice surface in an area with a size comparable to a single pixel of a modern digital camera. Our finding suggests the phonon-magnon interaction as a promising hardware basis for realizing on-chip reservoir computing in future neuromorphic architectures.

Ultrafast magnetoacoustics in Galfenol nanostructures

Phonons and magnons are prospective information carriers to substitute the transfer of charge in nanoscale communication devices. Our ability to manipulate them at the nanoscale and with ultimate speed is examined by ultrafast acoustics and femtosecond optomagnetism, which use ultrashort laser pulses for generation and detection of the corresponding coherent excitations. Ultrafast magnetoacoustics merges these research directions and focuses on the interaction of optically generated coherent phonons and magnons. In this review, we present ultrafast magnetoacoustic experiments with nanostructures based on the alloy (Fe,Ga) known as Galfenol. We demonstrate how broad we can manipulate the magnetic response on an optical excitation by controlling the spectrum of generated coherent phonons and their interaction with magnons. Resonant phonon pumping of magnons, formation of magnon polarons, driving of a magnetization wave by a guided phonon wavepacket are demonstrated. The presented experimental results have great application potential in emerging areas of modern nanoelectronics.