Exploiting the Momentum Distribution in Atomically Confined Plasmonic Fields by Inelastic Scatterings.

The utilization of atomically confined plasmonic fields has revolutionized the imaging technique. According to the fundamental position-momentum uncertainty principle, such a narrow spatial distribution certainly leads to a broad momentum distribution in the fields, which has however been overlooked. Here we propose a novel exploitation for the momentum distribution by adaptively satisfying the conservation law of momentum in inelastic Raman scatterings in periodic systems, providing a unique optical means of directly measuring the whole phonon dispersions. The proposed technique is particularly useful for measuring phonon dispersions of low-dimensional hydrogen-rich materials, which are completely inaccessible via other techniques. The numerical results for a single all-trans polyacetylene chain demonstrate that all phonon dispersion branches can be conclusively measured from their Raman images for the first time. Our findings highlight a unique advantage of the emerging momentum-based nanophotonics and open the door for exploiting highly confined plasmonic fields in another dimension.

Electronic Properties of Vanadium Atoms Adsorption on Clean and Graphene-Covered Cu(111) Surface.

The electronic properties of vanadium atoms adsorbed on clean and graphene-covered Cu(111) surface have been systematically studied using ab initio theoretical method. Two coverages (1/9 ML and 1 ML) of vanadium adsorption are considered in this work. Our calculations indicate that V staying underneath the Cu surface is found to be the most stable adsorption site at the aforementioned two coverages for V/Cu(111). However, such adsorption may lead to undesired properties. Therefore, we introduce graphene as a buffer layer to effectively alleviate the direct interaction between V and Cu surface. The calculations show that electronic properties of the original graphene layer are significantly affected by the interactions of C atoms with the V adatoms; the Dirac point of graphene is "destroyed" as a consequence at both coverages. In the V/Gra/Cu(111) system, the interaction between graphene layer and the substrate Cu atoms remains weak as in the Gra/Cu(111) system. Moreover, a relatively low coverage of 1/9 ML gives rise to a spin-polarized system while a non-spin-polarized system is observed at the coverage of 1 ML. This finding offers a new way for the application of vanadium-based materials in reality.