arXiv subjects

Kevin N. Moser

Publications and source records attributed to Kevin N. Moser.

3 recordsLinked to original sources

arXiv2026

Unified light-matter metric of molecular and nanophotonic chirality

Signatures of a material object's broken inversion symmetry within its intrinsic excitations and associated optical fields have largely evaded characterization from a perspective that evenly accounts for the inseparability between matter and field dynamics. Here, we formulate a complex-valued pseudoscalar chirality metric that is derived from the coupled electromagnetic and material governing equations, and demonstrate its resolution of the excitational chirality exhibited by the eigenmodes and eigenfields of a family of structurally chiral objects, including those with chirally connected enantiomeric states.

physics.optics↗

arXiv2026

Probing Plasmonic Oscillations in 2D Moiré Nanocrystal Superlattices by Low-Loss EELS

Electron energy loss spectroscopy (EELS) has been established as a powerful analytical technique for investigating the oxidation state, band structure, and dielectric properties of materials with exceptional spatial resolution. Inspired by twisted 2D materials, we utilize low-loss EELS to examine the plasmonic excitations in 2D moiré Au nanocrystal superlattices (NCSLs) formed by liquid-air interface self-assembly using a double-dipping method. This approach produces stacked hexagonal layers that can be twisted, forming moiré patterns in NCSLs whose twist angles are precisely measured via scanning transmission electron microscopy (STEM). Low-loss EELS effectively mitigates challenges arising from fabrication-induced non-uniformity and reveals a blue shift in plasmonic excitation when comparing single-layer, double-layer, and twisted configurations. This sharply contrasts with the optical spectroscopy measurements, which show an overall red shift relative to the EELS data. The high spatial resolution of STEM-EELS further demonstrates that twist-induced symmetry breaking strongly influences plasmonic behavior. Coupled dipole modeling explains the observed discrepancies: the electron beam excites out-of-plane polarization modes unavailable to optical probes, while optical measurements average over ensembles. Our findings highlight that EELS provides complementary information to optical spectroscopy for understanding how structural arrangements at the nanoscale influence collective electronic properties, advancing the design of plasmonic metamaterials.

cond-mat.mtrl-sci↗

arXiv2025

Conservation of optical chirality in nanoscale light-matter interactions: A study of the Born-Kuhn model system

Optical chirality density is a measure of the local handedness of electromagnetic fields. Like energy density, it may be absorbed or scattered through the interaction between light and matter. Here, we utilize the conservation of optical chirality to connect the parity and time-reversal symmetries of the intrinsic excitational eigenmodes of a material to those of their associated electromagnetic eigenfields as dictated by Maxwell's equations. To make this connection explicit, we theoretically examine the Born-Kuhn (BK) system, composed of a pair of plasmonic nanorods of variable separation, as a prototypical material model that is both geometrically chiral in its static structure and truly excitationally chiral in its eigenexcitations and eigenfields. By relaying optical chirality metrics of the BK eigenfields back to their underlying sourcing material degrees of freedom, we derive a unique mechanical chirality measure that is related to, but distinct from, other pseudoscalar metrics recently discussed in the literature. Beyond analysis in the absence of sources, we further derive optical chiral extinction, scattering, and absorption cross sections under external drive and discuss their rigorous connection to more common circular dichroism measurements as well as their limitations in comparison to eigenfield chirality metrics. Lastly, we investigate the conversion of achiral linearly polarized light into chiral elliptically polarized light through interaction with the BK system, illustrating the conservation of optical chirality in the interaction between light and matter through an analytically tractable example.

physics.optics↗