Active Metaspintronics (AMPERE)
Abstract
PUBLICLY RELEASABLE PROJECT ABSTRACT DoD Research and Education Program for W911NF-17-S-0002. Project: Active Metaspintronics (AMPERE). Principal Investigator: Prof. Marco Peccianti. A rapidly rising topic in ultrafast terahertz photonics is the investigation of spin-related physical processes in condensed matter systems. The possibility of triggering spin-transport with picosecond and sub-picosecond transient times has created an interesting contact point between ultrafast photonics and research on spin-orbit interactions. In spintronics, spin currents propagate as `pure? electron-spin perturbations which, generally, do not require an actual charge flow (as opposed to standard electronics based on real charge currents), enabling, for example, transfer and storage of information with reduced thermal dissipation. In an interesting class of systems, the establishment of charge currents leads to the generation of spin dynamics in magnetic media, also known as spin-Hall effect (SHE), which is generally caused by spin-orbit interactions. Quite interestingly, the inverse spin-Hall effect (ISHE) mediates the opposite conversion process, and it can be observed in non-magnetic media through the injection and splitting of polarized spin-currents resulting in transverse charge currents. A pivotal element to be added to this scenario is that terahertz waves provide a means for simultaneously interacting with carriers and spin waves. Interestingly, the need to detect local spin-currents triggered by ultrafast laser pulses led to the optimizations of structures supporting the ISHE, effectively triggering the emergence of novel spintronic ultrafast terahertz emitters, driven by ultrafast thermal perturbations. The connection between spintronics, terahertz emission, and their control with structured light has been established very recently in the framework of single-pixel imaging protocols. Key element in one of our investigations, the spatial resolution of such a control, lies on the scale of the optical diffraction limit, and it is not limited by the long terahertz wavelength. In these conditions, one can use a complete set of illumination patterns to explore and decompose in orthogonal spatial modes the terahertz near-field distribution. In this proposal, we investigate whether the mutual interaction between ultrafast thermal gradients and the conversion between spin-currents and charge-currents can be controlled through the suppression or enhancement of surface electromagnetic modes. To tackle this challenge, we propose to design and test an ensemble of tailored microstructures in a class of spintronics-metamaterials. Due to the small thickness scale compared to the optical wavelength, the spin-currents can couple with the near-field terahertz modes of the microstructures enabling complex field and spin-current geometries. Implementing a structured illumination is then key to selecting and enhancing specific spin-current modes inside the metamaterial. In summary, this project aims to explore theoretically and experimentally spin-current modal control based on ultrafast excitation with structured light of ISHE spintronic metasurfaces via detection of the generated terahertz electromagnetic transients.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 16, 2023
- Source ID
- W911NF2310313
Entities
People
- Marco Peccianti
Organizations
- Army Contracting Command
- Loughborough University
- United States Army