Adsorbate vibrational modes enhancement of radiative heat transfer and van der Waals friction

TL;DR

This paper investigates how adsorbates and surface plasmons can significantly enhance radiative heat transfer and van der Waals friction between solids at nanometer separations, with potential for measurable effects using current technology.

Contribution

It reveals the mechanisms of resonant photon tunneling via adsorbate vibrational modes and surface plasmons that lead to large enhancements in heat transfer and friction at small distances.

Findings

Heat transfer and van der Waals friction can increase by orders of magnitude due to adsorbates.

Resonant photon tunneling between vibrational modes causes the enhancement.

Van der Waals friction can be measured at 10 nm separation with current equipment.

Abstract

We study the dependence of the heat transfer and the van der Waals friction between two semi-infinite solids on the dielectric properties of the bodies. We show that the heat transfer and van der Waals friction at short separation between the solids may increase by many orders of magnitude when the surfaces are covered by adsorbates, or can support low-frequency surface plasmons. In this case the heat transfer and van der Waals friction are determined by resonant photon tunneling between adsorbate vibrational modes, or surface plasmon modes. The enhancement of the van der Waals friction is especially large when in the adsorbed layer there is an acoustic branch for the vibrations parallel to the surface like in the case of Cs adsorption on Cu(100) surface. In this case we show that even for separation $d=10$nm, the van der Waals friction induced by adsorbates can be so large that it can be measured with the present state-of-art equipment. The van an der Waals friction is characterized by a strong distance dependence ($\sim 1/d^6$), and at the small distances it can be much larger than \textit{the electrostatic} friction observed in \cite{Stipe}. \vskip 0.3cm \textit{Keywords}: non-contact friction, van der Waals friction, radiative heat transfer, atomic force microscope, adsorbate vibrational mode