Capacitor physics in ultra-near-field heat transfer

Using the nonequilibrium Green's function (NEGF) formalism, we propose a microscopic theory for near-field heat transfer between charged metal plates focusing on the Coulomb interactions. Tight-binding models for the electrons are coupled to the electromagnetic field continuum through a scalar potential. Our approach differs from the established ones based on Rytov fluctuational electrodynamics, which deals with the transverse radiative field and vector potential. For a two quantum-dot model a new length scale emerges below which the heat current exhibits great enhancement. This length scale is related to the physics of parallel plate capacitors. At long distances $d$, the energy flux decreases as $1/d^2$.