Radiative exchange of heat between nanostructures

Surfaces in close proximity exchange heat through evanescent photon tunnelling modes as well as by freely propagating modes. These additional near field contributions to radiation scale with separation, d, between surfaces as d-2 and are dominant at spacings d<<T, a typical wavelength at temperature T. We calculate simple expressions for the photon tunnelling and find that there are drastic effects in many nanostructured systems, for example in the scanning tunnelling microscope. The results are linked to quantum information theory which dictates that the maximum heat tunnelling current in any one channel is determined by the temperature alone. Consequences for the scanning tunnelling microscope are discussed, where a hot tip may cause intense local heating of a surface without actually being in physical contact, hence desorbing molecular species, or even modifying the surface itself: a possible extension of the STM's capacity for surface modification. A further extension of this concept is proposed in the form of a `heat stamp' capable of delivering a high definition pattern of heat to a second surface.