Theoretical Foundations of Goldene Plasmonics

The recent experimental realization of goldene, an atomically thin form of gold, provides a unique platform to investigate collective electronic excitations in the ultimate two-dimensional (2D) limit of a noble metal. Here we reveal that goldene is a plasmonic material whose collective response is strongly shaped by its reduced dimensionality and underlying electronic structure. Using first-principles many-body calculations, we show that monolayer goldene supports intrinsic acoustic and optical plasmons arising from the interplay between the low-energy metallic response and dispersive s and more localized d states. As the number of layers increases, interlayer coupling and enhanced screening progressively quench this directional anisotropy, driving the system toward the isotropic response of bulk gold. In finite nanostructures, the plasmonic resonance follows the size scaling characteristic of confined 2D metallic systems. Our results establish the foundations of goldene plasmonics, with technological implications for nanophotonic sensing, photocatalysis, and atomically thin optoelectronic devices.