# Spin-Momentum Locking in the Near Field of Metal Nanoparticles

## TL;DR

This paper investigates how the spin of light interacts with and influences the momentum in the near field of metal nanoparticles, revealing spin-momentum locking phenomena that could impact nano-optics and nano-photonics applications.

## Contribution

It demonstrates the presence of spin-momentum locking in the near field of localized surface resonances in metal nanostructures, a novel insight into light behavior at the nanoscale.

## Key findings

- Spin of incident light controls the rotation of canonical momentum.
- Localized surface resonances exhibit spin-momentum locking.
- Near-field enhancement enables subwavelength light confinement.

## Abstract

Light carries both spin and momentum. Spin-orbit interactions of light come into play at the subwavelength scale of nano-optics and nano-photonics, where they determine the behaviour of light. These phenomena, in which the spin affects and controls the spatial degrees of freedom of light, are attracting rapidly growing interest. Here we present results on the spin-momentum locking in the near field of metal nanostructures supporting localized surface resonances. These systems can confine light to very small dimensions below the diffraction limit, leading to a striking near-field enhancement. In contrast to the propagating evanescent waves of surface plasmon-polariton modes, the electromagnetic near-field of localized surface resonances does not exhibit a definite position-independent momentum or polarization. Our results can be useful to investigate the spin-orbit interactions of light for complex evanescent fields. Note that the spin of the incident light can control the rotation direction of the canonical momentum.