Spin-momentum locking breakdown on plasmonic metasurfaces

TL;DR

This paper develops a scattering formalism to analyze spin-momentum locking in plasmonic metasurfaces, revealing how certain configurations and symmetries cause breakdowns in the locking effect, exemplified by surface plasmon polaritons.

Contribution

It introduces a universal scattering formalism for analyzing spin-momentum locking in holey plasmonic metasurfaces considering arbitrary hole arrangements and orientations.

Findings

Spin-momentum locking depends on unit cell configuration.

Breakdowns occur due to specific symmetry and configuration terms.

Surface plasmon polaritons exhibit notable spin-momentum locking breakdown.

Abstract

We present a scattering formalism to analyze the spin-momentum locking in structured holey plasmonic metasurfaces. It is valid for any unit cell for arbitrary position and orientation of the holes. The spin-momentum locking emergence is found to originate from the unit cell configuration. Additionally, we find that there are several breakdown terms spoiling the perfect spin-momentum locking polarization. We prove that this breakdown also appears in systems with global symmetries of translation and rotation of the whole lattice, like the Kagome lattice. Finally, we present the excitation of surface plasmon polaritons as the paramount example of the spin-momentum locking breakdown.