Ida Juliane Bundgaard

arXiv2026

Structural Colours with Transition Metal Dichalcogenide Nanostructures

We introduce transition metal-dichalcogenide (TMD) nanostructures as a promising platform for the realisation of structural colours. Processing of semianalytically calculated reflectance spectra of TMD nanosphere arrays shows a wide range of colours, which are obtained simply through tailoring the radius and separation of spheres in the array, with the size-dependent Mie modes of the nanoparticles being the primary contributor to the spectra. Additionally, it is demonstrated that further coverage of the colour space can be obtained by employing different materials or different lattice unit cells. Theoretical examination of the impact of the excitonic attributes of TMDs on the resulting structural colours indicates that self-hybridisation between nanoparticle modes and excitonic transitions may be employed for further tuneability. Moreover, the impact of TMD anisotropy on the structural colours is shown to be negligible for small structures at typical viewing angles, while the viewing angle itself may impact the colour. This work sets out to be a general investigation of TMD nanoarchitectures, with a focus on nanosphere arrays, for structural colours, by examining both inherent material features through the lens of colourimetry, and the ability of such structures to sustain a broad range of hues.

cond-mat.mes-hall↗

arXiv2023

Quantum-informed plasmonics for strong coupling: the role of electron spill-out

The effect of nonlocality on the optical response of metals lies at the forefront of research in nanoscale physics and, in particular, quantum plasmonics. In alkali metals, nonlocality manifests predominantly as electron density spill-out at the metal boundary, and as surface-enabled Landau damping. For an accurate description of plasmonic modes, these effects need be taken into account in the theoretical modelling of the material. The resulting modal frequency shifts and broadening become particularly relevant when dealing with the strong interaction between plasmons and excitons, where hybrid modes emerge and the way they are affected can reflect modifications of the coupling strength. Both nonlocal phenomena can be incorporated in the classical local theory by applying a surface-response formalism embodied by the Feibelman parameters. Here, we implement surface-response corrections in Mie theory to study the optical response of spherical plasmonic--excitonic composites in core--shell configurations. We investigate sodium, a jellium metal dominated by spill-out, for which it has been anticipated that nonlocal corrections should lead to an observable change in the coupling strength, appearing as a modification of the width of the mode splitting. We show that, contrary to expectations, the influence of nonlocality on the anticrossing is minimal, thus validating the accuracy of the local response approximation in strong-coupling photonics.

cond-mat.mes-hall↗