  Above-light-line surface plasmon polaritons can arise at the interface
between a metal and epsilon-near-zero metamaterial. This unique feature induces
unusual fast-wave non-radiative modes in a epsilon-near-zero material/metal
bilayer. Excitation of this peculiar mode leads to wide-angle perfect
absorption in low-loss ultrathin metamaterials. The ratio of the perfect
absorption wavelength to the thickness of the epsilon-near-zero metamaterial
can be as high as 10^4; the electromagnetic energy can be confined in a layer
as thin as {\lambda}/10000. Unlike conventional fast-wave leaky modes, these
fast-wave non-radiative modes have quasi-static capacitive features that
naturally match with the space-wave field, and thus are easily accessible from
free space. The perfect absorption wavelength can be tuned from mid- to
far-infrared by tuning the epsilon = 0 wavelength while keeping the thickness
of the structure unchanged.
