FALCON: Femtosecond non-dissipAtive propagation controL and charge Conversion of THz antiferrOmagnetic magnoNs

• Applicant: Dr. Davide Bossini
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431136326

The massively increasing demand of data storage and processing is predicted to be non-sustainable for the current information technology, which has reached a bottleneck. Alternative strategies to perform logic operations and transfer information in a faster and more energy-efficient way than in nowadays charge-based scheme have to be developed. It has been proposed that spin waves, which are collective spin excitations of a magnetic material, can be employed as information carriers, which would allow operations with vectorial (wave) rather than scalar (charge) variables. Relying on waves would provide an additional degree of freedom for computations, namely the phase. A promising approach to the establishment of spin waves computation schemes, able to outperform the charge-based technology in terms of operational speed and energy consumption, relies on the use of ultrashort (i.e. femtosecond - fs-) laser pulses. In fact, the optical stimulus requires neither electric contacts nor electronic currents in a material: it can be applied to semiconductors and insulators with band-gap bigger than the photon-energy, so that neither Joule heating nor a massive laser-heating occur. The best candidate materials for ultrafast and non-dissipative (i.e. energy-efficient) computational schemes based on spin waves have been identified in dielectric and semiconductor antiferromagnets (AFs): this magnetic order naturally provides high-frequency spin waves entering the THz regime. Pioneer investigations have already demonstrated that in a single portion of an AF, spin waves can be generated and controlled on extreme time-scales and with negligible energy dissipations. The space-propagation of such spin waves in AFs, which is the essence of information-transfer, and the possibility to convert the magnetic signal into a charge signal (necessary for the integration with nowadays technology) have been hitherto barely investigated. FALCON aims at bridging the gap in fundamental knowledge concerning the propagation dynamics of spin waves and their conversion to electric signals in AFs. This ambitious goal requires first to develop a novel instrument, namely a magneto-optical microscope able to image the time- and space-resolved spin wave dynamics with fs time- and nm-space resolutions. Once the optical generation and detection of the spin waves propagation dynamics will have been established, the control of such signal will be demonstrated. Not only the amplitude and phase of the spin waves will be manipulated on extreme time- and length-scales, but also the direction of propagation, thus developing a waveguiding concept for spin waves in AFs. Finally, a novel experimental scheme will be developed merging the optical excitation with the detection of photo-emitted electrons. This approach will allow to unravel the influence of propagating spin waves on the electronic band structure, measured with fs time-, μm space- and even spin-resolution.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Laser system
• Instrumentation Group: 5700 Festkörper-Laser