Hyperbolic metamaterials as an analog of a blackbody in the near field.

We study the near-field heat exchange between hyperbolic materials and demonstrate that these media are able to support broadband frustrated modes which transport heat by photon tunneling with a high efficiency close to the theoretical limit. We predict that hyperbolic materials can be designed to be perfect thermal emitters at nanoscale and derive an upper limit for the heat flux due to hyperbolic modes.