# Quantum plasmonics

We are all familiar with electronic devices, which exploit the possibility to control the electron flux in metals and semiconductors. Plasmonic devices also take advantage of the electron motion in metals. However, this is a very peculiar kind of motion which originates from the coherent oscillations of many electrons, also known as plasmons. Surface plasmons are oscillations which take place at the interface between a metal and a dielectric (i.e., air) and they can be easily generated and controlled using a laser. For this reason, plasmonic devices are good candidates for faster (i.e., terahertz) and smaller (i.e., nanoscale) components for cheap and reliable communication technologies.

To faithfully model the plasmonic response at the nanoscale, we use a simple and robust jellium approximation along with a Time-Dependent Density-Functional Theory (TDDFT) description of the electron dynamics. Hence, we can include the contributions from the quantum delocalisation of the electron in a transferable and unbiased way (in collaboration with P. Zhang, F.J. García Vidal, and P. García Gonzalez). Our method scales favourably with the size of the system and is suited to model the plasmonic response of systems beyond the possibilities of atomistic simulations.

**Relevant Papers**

**Title:** Performance of Nonlocal Optics When Applied to Plasmonic Nanostructures

**Authors:** Stella L., Zhang P., Garcia-Vidal F.J., Rubio A., Garcia-Gonzalez P.

**Journal:** *Journal of Physical Chemistry C*, **117**, No. 17, pp. 8941-8949 (2 May 2013)

*Field enhancement between a pair of sodium nanowires. At variance with classical local and semi-local approximations, the jellium/TDDFT approach yields an enhancement localised in the gap between the nanowires. This is a consequence of the quantum delocalisation of the electrons. *