Tunneling of two-dimensional surface polaritons through plasmonic nanoplates on atomically thin crystals.

We theoretically investigate the tunneling of two-dimensional surface polaritons (2DSPs) through plasmonic nanoplates on atomically thin crystals. By developing an analytic model based on coupled-mode theory, we examine the tunneling efficiency as a function of the plate's width and height. Our analysis reveals that the tunneling is mediated by evanescent waves induced near the plate edges due to interactions between 2DSPs and the plate, enabling the consistent recoupling of 2DSPs across plates of finite width, regardless of their height. Additionally, we clarify that these evanescent waves not only facilitate tunneling but also induce an anomalous phase shift in the 2DSPs reflected from the plate. This phase shift is shown to play a critical role in the resonant tunneling of 2DSPs through two plates, effectively creating a polariton-assisted resonator in the deep subwavelength regime.