  Plasmon resonance in nanopatterned single layer graphene nanoribbon (SL-GNR),
double layer graphene nanoribbon (DL-GNR) and triple layer graphene nanoribbon
(TL-GNR) structures is studied both experimentally and by numerical
simulations. We use 'realistic' graphene samples in our experiments to identify
the key bottle necks in both experiments and theoretical models. The existence
of electrical tunable plasmons in such stacked multilayer GNRs was first
experimentally verified by infrared microscopy. We find that the strength of
the plasmonic resonance increases in DL-GNR when compared to SL-GNRs. However,
we do not find a further such increase in TL-GNRs compared to DL-GNRs. We
carried out systematic full wave simulations using finite element technique to
validate and fit experimental results, and extract the carrier scattering rate
as a fitting parameter. The numerical simulations show remarkable agreement
with experiments for unpatterned SLG sheet, and a qualitative agreement for
patterned graphene sheet. We believe that further improvements such as
introducing a bandgap into the numerical model could lead to a better
quantitative agreement of numerical simulations with experiments. We also note
that such advanced modeling would first require better quality graphene samples
and accurate measurements.
