Radiative heat transfer as a Landauer-B\"{u}ttiker problem

We study the radiative heat transfer between two semi-infinite half-spaces, bounded by conductive surfaces in contact with vacuum. This setup is interpreted as a four-terminal mesoscopic transport problem. The slabs and interfaces are viewed as bosonic reservoirs, coupled perfectly to a scattering center consisting of the two interfaces and vacuum. Using Rytov's fluctuational electrodynamics and assuming Kirchhoff's circuital law, we calculate the heat flow in each bath. This allows for explicit evaluation of a conductance matrix, from which one readily verifies B\"{u}ttiker symmetry. Thus, radiative heat transfer in layered media with conductive interfaces becomes a Landauer-B\"{u}ttiker transport problem.