Selection of Hydrodynamic Models for the Nonlocal Response of Plasmonic Nanotopologies

Much attention has been attracted by the nonlocal hydrodynamic model, which provides the first-order approximation of non-classical effects, essentially governing the light-matter interaction at deep-nanometer scale. Several hydrodynamic models, together with additional boundary conditions, have been introduced to describe the behavior of the free electron gas in metals. This work investigates the performance of the following models: the hard wall hydrodynamic model (HW-HDM), the quantum hydrodynamic model (Q-HDM), the curl-free hydrodynamic model, and the shear forces hydrodynamic model. The analysis is conducted for the mode structure (natural or quasi-normal modes) of a canonical spherical nanoparticle. In contrast to HW-HDM and Q-HDM, the other two models break down, due to artifactual mode interference.