Giant near-field mediated heat flux at the nanometer scale

In this Letter, we report on quantitative measurements of the absolute near-field mediated heat flux between a gold coated near-field scanning thermal microscope (NSThM) tip and a planar gold sample at nanometer distances of 0.2 nm- 7 nm. We find an extraordinary large heat flux which is more than five orders of magnitude larger than black-body radiation and four orders of magnitude larger than the values predicted by conventional theory of fluctuational electrodynamics. Additionally, we compare our data with different theories of phonon tunneling which might explain a drastically increased heat flux, but are found not to be able to reproduce the distance dependence observed in our experiment. The findings demand modified or even new models of heat transfer across vacuum gaps at nanometer distances.