# Modal analysis for nanoplasmonics with nonlocal material properties

## TL;DR

This paper develops contour integral methods to compute eigenfrequencies and resonant states in nanoplasmonic systems with nonlocal material properties, enabling detailed modal analysis of nanowires.

## Contribution

It introduces a novel approach for modal analysis in nonlocal plasmonic systems using contour integral techniques, advancing the understanding of nanoplasmonic resonances.

## Key findings

- Computed all complex eigenfrequencies for a nanowire across a broad frequency range.
- Identified resonant states relevant for the nanowire's extinction cross section.
- Demonstrated the effectiveness of the method for nonlocal hydrodynamic Drude models.

## Abstract

Plasmonic devices with feature sizes of a few nanometers exhibit effects which can be described by the nonlocal hydrodynamic Drude model. We demonstrate how to exploit contour integral methods for computing eigenfrequencies and resonant states of such systems. We propose an approach for deriving the modal expansion of relevant physical observables. We use the methods to perform a modal analysis for a metal nanowire. All complex eigenfrequencies in a large frequency range and the corresponding resonant states are computed. We identify those resonant states which are relevant for the extinction cross section of the nanowire.