Quantum plasmonics: from jellium models to ab initio calculations

Light-matter interaction in plasmonic nanostructures is often treated within the realm of classical optics. However, recent experimental findings show the need to go beyond the classical models to explain and predict the plasmonic response at the nanoscale. A prototypical system is a nanoparticle dimer, extensively studied using both classical and quantum prescriptions. However, only very recently, fully ab initio time-dependent density functional theory (TDDFT) calculations of the optical response of these dimers have been carried out. Here, we review the recent work on the impact of the atomic structure on the optical properties of such systems. We show that TDDFT can be an invaluable tool to simulate the time evolution of plasmonic modes, providing fundamental understanding into the underlying microscopical mechanisms.We thankfully acknowledge the financial support by the European Research Council (ERC-2010-AdG Proposal No. 267374 and ERC-2011-AdG Proposal No. 290891), the Spanish Government (grants MAT2011-28581-C02-01, FIS2013-46159-C3-1-P, and MAT2014-53432-C5-5-R), the Basque Country Government (Grupos Consolidados IT-57813), and COST Action MP1306 (EUSpec)]. PGG, JF, and FJGV acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the "Maria de Maeztu" Programme for Units of Excellence in R&D (MDM-2014-0377). We also appreciate the technical support by Joseba Alberdi-Rodrguez and fruitful discussions with Javier Aizpurua, Garnett Bryant, Juan Carlos Cuevas, Stefano Corni, Antonio Fernandez-Domnguez, Elisa Molinari, Carmina Monreal, Risto Nieminen, Daniel Sanchez-Portal, Lorenzo Stella, Hans-Christian Weissker, and Pu Zhang