Inducing an Incipient Terahertz Finite Plasmonic Crystal in Coupled Two Dimensional Plasmonic Cavities

Abstract

We measured a change in the current transport of an antenna-coupled, multi-gate, GaAs/AlGaAs field-effect transistor when terahertz electromagnetic waves irradiated the transistor and attribute the change to bolometric heating of the electrons in the two-dimensional electron channel. The observed terahertz absorption spectrum indicates coherence between plasmons excited under adjacent biased device gates. The experimental results agree quantitatively with a theoretical model we developed that is based on a generalized plasmonic transmission line formalism and describes an evolution of the plasmonic spectrum with increasing electron density modulation from homogeneous to the crystal limit. These results demonstrate an electronically induced and dynamically tunable plasmonic band structure.

Transmission line theory of collective plasma excitations in periodic two-dimensional electron systems: Finite plasmonic crystals and Tamm states

“…The crystal can be terminated either by the Ohmic contact or by the infinite barrier on each side. To make our calculations more relevant to the recent experimental work [31] we assume that 2DEG in the ungated regions is still screened by the neighboring gates and surrounding metallization but 2D electron density can be tuned in the gated regions only. In this model, both and are determined by Eqs.…”

“…(7) as well as spatial distributions of the in-plane electric potential, current and charge density of the plasma wave [31]. Additional complications in the TL formulation of the 2D plasmon theory arise from the non-TEM character of the 2D plasma mode.…”

“…Our theory is also applicable to a broader class of piecewise 2D electron systems in semiconductor nanostructures. Some key elements of the theory have already been used for interpretation of experimental data in our recently published experimental study of a spatially inhomogeneous 2D plasmonic cavity [31].…”

“…[30] the band gaps have been found in the energy spectrum of edge magnetoplasmons. In one of the latest developments, the tunable band spectrum of the finite plasmonic crystal formed in the plasmonic cavity of GaAs/AlGaAs FETs has been measured at sub-THz frequencies [31].…”

“…These modes are excited when an incident EM wave is coupled to the 2DEG by a grating gate and are probed in transmission and absorption experiments. In the recent experiments an energy spectrum of plasmonic crystal was probed in the plasmonic cavities [31] or waveguides [26] where a variety of plasma modes can be excited. The full energy band structure of the finite plasmonic crystal should be used for interpretation of these experiments.…”