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Light-matter interaction at the atomic scale rules fundamental phenomena such as photoemission and lasing, while enabling basic everyday technologies, including photovoltaics and optical communications. In this context, plasmons -the collective electron oscillations in conducting materials-are important because they allow manipulating optical fields at the nanoscale. The advent of graphene and other two-dimensional crystals has pushed plasmons down to genuinely atomic dimensions, displaying appealing properties such as a large electrical tunability. However, plasmons in these materials are either too broad or lying at low frequencies, well below the technologically relevant nearinfrared regime. Here we demonstrate sharp near-infrared plasmons in lithographically-patterned wafer-scale atomically-thin silver crystalline films. Our measured optical spectra reveal narrow plasmons (quality factor ∼ 4), further supported by a low sheet resistance comparable to bulk metal in few-atomic-layer silver films down to seven Ag(111) monolayers. Good crystal quality and plasmon narrowness are obtained despite the addition of a thin passivating dielectric, which renders our samples resilient to ambient conditions. The observation of spectrally sharp and strongly confined plasmons in atomically thin silver holds great potential for electro-optical modulation and optical sensing applications. * These two authors contributed equally to the work. † Electronic address: enrique.ortega@ehu.es ‡ Electronic address: javier.garciadeabajo@icfo.es arXiv:1901.07739v2 [cond-mat.mes-hall]

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Curved crystal surfaces enable the systematic and accurate comparison of physical and chemical processes for a full set of vicinal crystal planes, which are probed in the very same environment. Here, we examine the early stages of the CO chemisorption on vicinal Rh(111) surfaces using a curved Rh crystal that exposes a smoothly variable density of {100} (A-type) and {111} (B-type) steps. We readily identify and quantify step and terrace species by resolving their respective core-level lines using X-ray photoelectron spectroscopy at different locations on the curved surface. Uptake experiments show similar sticking probabilities at all surface planes, subtle asymmetries between A- and B-type steps, and significantly lower saturation coverage at densely stepped surfaces as compared to the (111) plane. The analysis of the C 1s intensity variation across the curved sample allows us to discuss the adsorption geometry around the step edge.