Microscopic analysis of the energy, momentum and spin distributions in a surface plasmon-polariton wave

TL;DR

This paper provides a detailed microscopic analysis of the energy, momentum, and spin distributions in surface plasmon-polariton waves at a metal-dielectric interface, revealing nanoscale structures with potential nanotech applications.

Contribution

It introduces a hydrodynamic electron-gas model for analyzing electromagnetic field distributions near SPPs, including a novel spin-orbital momentum decomposition method in charged media.

Findings

Analytical and numerical energy, spin, and momentum distributions near SPPs.

Identification of physical origins of field and material contributions.

Discovery of nanoscale structures in SPP energy and momentum distributions.

Abstract

We analyze the electromagnetic field near a plane interface between a conductive and a dielectric media, under conditions supporting surface plasmon-polariton (SPP) propagation. The conductive medium is described by the hydrodynamic electron-gas model that enables a consistent analysis of the field-induced variations of the electron density and velocity at the interface and its nearest vicinity. The distributions of electromagnetic dynamical characteristics: energy, energy flow, spin and momentum are calculated analytically and illustrated numerically, employing silver-vacuum interface as an example. A set of the "field" and material contributions to the energy, spin and momentum are explicitly identified and classified with respect to their physical origins and properties, and the orbital (canonical) and spin (Belinfante) momentum constituents are separately examined. In this context, a procedure for the spin-orbital momentum decomposition in the presence of free charges is proposed and substantiated. The microscopic results agree with the known phenomenological data but additionally show specific nanoscale structures in the near-interface behavior of the SPP energy and momentum, which can be deliberately created, controlled and used in nanotechnology applications.