Super-Planckian far-field radiative heat transfer
08/01/18 14:28
Understanding heat exchange via thermal radiation is key for many areas of science and engineering. Radiative heat transfer between closely placed objects, with separations smaller than the thermal wavelength (around 10 microns at room temperature), is attracting a lot of attention because of the possibility to overcome the classical limit set by Planck law. However, in the far-field regime, when gaps are larger than the thermal wavelength, thermal radiation is supposed to be well understood and no super-Planckian heat transfer has been reported. In this work we present a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. We illustrate this phenomenon in micron-sized dielectric structures, the so-called suspended pads, that can be readily fabricated and tested with existing technology. Our work shows the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nano-devices.
