Can Copper Nanostructures Sustain High-Quality Plasmons?

Silver is considered to be the king among plasmonic materials because it features low inelastic absorption in visible and infrared (vis-IR) spectral regions compared other metals. In contrast, copper commonly regarded as being too lossy for applications. Here, we experimentally demonstrate vis-IR plasmons long nanowires (NWs) with quality factors that exceed a value of 60, determined by spatially resolved, high-resolution electron energy-loss spectroscopy (EELS) measurements. We explain this counterintuitive result fact these metal wires have most their electromagnetic energy outside metal, thus, they are less sensitive losses material. present an extensive set data acquired on silver NWs varying diameters supporting conclusion further allowing us understand relative roles played radiative nonradiative span wide range energies down $<20\,$meV. At such small plasmon energies, thermal population modes becomes significant enough enable observation gains associated events. Our results support use attractive cheap abundant material platform high elongated nanostructures.