Progress in the optical response of crystalline atomically thin films

Recent progress in the fabrication of metallic thin films allows for a precise control of the surface crystallographic orientation and thickness, turning them to be a great appeal in plasmonic devices. Considering such a crystalline quality and going towards smaller optical designs; surface, nonlocal, and quantum finite-size effects play a major role in metallic thin films when interacting with light. Here we explore various strategies to seek for the linear and nonlinear optical response manifested in a variety of scenarios and configurations which are based on precise quantum-mechanical formalisms that describe the dynamics of electrons in such films, e.g. EELS, Feibelman d-parameters, periodic- and finite-systems, etc. We believe that our results can inspire future devices based on crystalline metal films as well as motivate further numerical implementation strategies.