Modification of response properties of the Be(0001) surface upon adsorption of a potassium monolayer: An ab initio calculation

Abstract

Collective electronic excitations associated with a potassium monolayer (1 ML) on a Be(0001) substrate are studied using ab initio evaluations of the surface response function with the use of energies and wave functions obtained from the selfconsistent pseudopotential calculations. The plasmon dispersion relations as well as real and imaginary parts of the dynamical induced charge density oscillations are presented. Comparison of the collective modes of the 1 ML K/Be(0001) system with that of a clean Be(0001) surface is given. It is shown that the K monolayer adsorption leads to appearance, additionally to the conventional surface plasmon of a clean Be surface, of a low-energy mode with characteristic acoustic-like dispersion in the 0-2 eV energy range. The existence of this mode owes to the presence of a K-induced quantum-well-state band whose wave function is strongly localized in the K adlayer. Also we observe a K-derived multipole plasmon with energy around 3 eV. Some other modifications in the Be surface plasmon properties upon K adsorption are discussed as well. 1 Introduction The study of electronic excitations in thin adsorbed alkali metal layers was an active topic for more than four decades . These systems are of interest because they show variety of phenomena such as work function changes, metal-insulator transitions, and surface reconstruction. In particular, they allow to investigate in great details the evolution of various basic physical properties of metal surfaces by changing the alkali adatom coverage. Thus the change in the screening properties (in particular, the strong non-locality of the screened interaction) at the surfaces in general [24]

The influence of electron confinement, quantum size effects, and film morphology on the dispersion and the damping of plasmonic modes in Ag and Au thin films

“…Shockley surface states existing at the (1 1 1) surfaces of noble metals [56,149,[366][367][368][369][370][371][372][373][374] support this collective excitation, which owes its existence to the spatial coexistence of a 2DEG with a 3D electron gas. In Ag the excitation is ascribed to the screening of the Shockley surface states electrons by bulk electrons [367,375], while recent results have indicated that in both Au [150] and Cu [376] the opposite phenomenon occurs: slow bulk electrons are screened by the faster surface state electrons.…”

Oxygen vibrations and acoustic surface plasmon on Be(0001)

“…At present alkali-metal adsorption on Be(0001) has been shown to distort the dispersion due to induced quantum well states. [28][29][30] It has been demonstrated in Ref. 16 that increasing exposure of Be(0001) to O 2 leads to a shift of the surface plasmon energy and a decrease of its intensity in vibration spectra acquired along the¯ M direction of the surface Brillouin zone.…”

Quantum mechanical study on plasmon resonances in small ring clusters

“…During the past few decades, plasmonic excitations in nanostructures have attracted much attention in nanosciences,1–20 because they have given rise to a large number of optical applications ranging from waveguiding to chemical and biological sensing and to medical applications, such as photothermal ablation of cancer cells and tumors. Among these nanostructures, ring structures, with their inherent high degree of symmetry, continue to fascinate scientists in a wide range of disciplines 21–30.…”