  Metamaterials possess artificial bulk and surface electromagnetic states.
Tamed dispersion properties of surface waves allow one to achieve controllable
super-Planckian radiative heat transfer (RHT) process between two closely
spaced objects. We numerically demonstrate enhanced RHT between two 2D grooved
metal plates by a full-wave scattering approach. The enhancement originates
from both transverse magnetic spoof surface plasmon polaritons and a series of
transverse electric bonding- and anti-bonding waveguide modes at surfaces. The
RHT spectrum is frequency-selective, and highly geometrically tailorable. Our
simulation also reveals thermally excited non-resonant surface waves in
constituent materials can play a prevailing role for RHT at an extremely small
separation between two plates, rendering metamaterial modes insignificant for
the energy transfer process.
