  Resonant tunneling of surface polaritons across a subwavelength vacuum gap
between two polar or metallic bodies at different temperatures leads to an
almost monochromatic heat transfer which can exceed by several orders of
magnitude the far-field upper limit predicted by Planck's blackbody theory.
However, despite its strong magnitude, this transfer is very far from the
maximum theoretical limit predicted in near-field. Here we propose an amplifier
for the photon heat tunneling based on a passive relay system intercalated
between the two bodies, which is able to partially compensate the intrinsic
exponential damping of energy transmission probability thanks to three-body
interaction mechanisms. As an immediate corollary, we show that the exalted
transfer observed in near-field between two media can be exported at larger
separation distances using such a relay. Photon heat tunneling assisted by
three-body interactions enables novel applications for thermal management at
nanoscale, near-field energy conversion and infrared spectroscopy.
