Quantum and nonlocal phenomena in plasmonic nanostructures
Plasmonics is commonly explored and interpreted within the framework of classical electrodynamics. On the other hand, with the increasing ability to explore plasmons in nanostructures with yet smaller characteristic dimensions, intrinsic length scales of the electron gas are anticipated to manifest in a nonlocal plasmonic response and other quantum corrections to the light-matter interactions. Efforts to make semi-classical hydrodynamic extensions of the Drude model will be addressed, as well as developments beyond these simplified models. In nanoparticles, nonlocal response promotes frequency blueshifts and nonlocal damping of high-order modes, as has been observed in single-particle EELS. As to the quantum mechanical origin of these effects, one can quantify the degree of nonclassical effects from an energy perspective. This provides a direct link between the experimentally observed resonance blueshift and the fraction of electromagnetic energy attributed to quantum degrees of freedom. Finally, implications of nonlocal dynamics for both classical and quantum optical problems in nanoplasmonics will be discussed.