Plasmonic capacitance and profiling the energy distribution of plasmonic hot electrons in planar metal-dielectric structures

Propagation of plasmonic excitations in metal-dielectric structures is always accompanied by the loss which includes the generation of hot electrons in the vicinity of the metal surface. This results in the formation of a 2-D hot electron gas in the metal slab. Here, we theoretically show that in a metal-insulator-metal (MIM) capacitor, which is under an applied AC bias, the plasmonic-hot electrons are trapped by the interface states existing in the interfacial region of the dielectric slab leading to the creation of “plasmonic-capacitance”; an increase in the capacitance of the MIM configuration due to the charge of interface that reveals dependence on the frequency of the AC bias. This dependency is used to profile the energy distribution of the plasmonic-hot electrons. Importantly, the obtained energy distribution can be employed as the signature of the plasmonic excitation. The approach we introduce in this work suggests a new way to study all types of plasmonic phenomena occurring in planar hyperbolic metamaterials including high-k hyperbolic plasmons and epsilon near zero modes.