Mie-enhanced micro-focused Brillouin light scattering with wavevector resolution

TL;DR

This paper introduces a novel optical technique using dielectric nanoresonators to achieve full wavevector resolution in Brillouin light scattering, enabling the measurement of previously inaccessible magnons and other excitations.

Contribution

The authors develop a method to tailor light in Brillouin scattering with nanoresonators, allowing measurement of spin waves with wavevectors between 30 and 300 rad/μm, filling a significant experimental gap.

Findings

Achieved wavevector resolution in Brillouin light scattering.

Enabled measurement of magnons with previously inaccessible wavevectors.

Potential applications in magnonics, phononics, and mechanobiology.

Abstract

Magnons, the quanta of spin waves, are magnetic excitations of matter spanning through the entire crystal's Brillouin zone and covering a wide range of frequencies ranging from sub-gigahertz to hundreds of terahertz. Magnons play a crucial role in many condensed matter phenomena, such as the reduction of saturation magnetization with increasing temperature or Bose-Einstein condensation. However, current experimental techniques cannot resolve magnons with wavevectors between 30 and 300$\,$rad$\,\mu$m$^{-1}$. In this letter, we address this gap by tailoring the light in Brillouin light scattering process with dielectric periodic nanoresonators and thus gaining access to the previously unmeasurable spin waves with full wavevector resolution using table-top optical setup. Filling this gap can stimulate further experimental investigations of the fundamental phenomena associated with magnons but also stimulate the application of magnonics in computational and microwave devices. In addition, the same methodology can be applied to other excitations of matter, such as phonons, opening up new possibilities in e.g. mechanobiological studies.