2013 Articles

Theory of thermal nonequilibrium entropy in near-field thermal radiation

Narayanaswamy, Arvind; Zheng, Yi

We propose a theoretical formalism to evaluate the entropy density and entropy flux that takes into account near-field effects, i.e., interference, diffraction, and tunneling of waves. Using the fluctuation-dissipation theorem, expressions for entropy density and entropy flux in a vacuum cavity between planar multilayered media are derived in terms of local density of photons, local density of accessible microscopic states, and velocity of energy transmission. The proposed method is used to determine the maximum work that can be extracted and a thermodynamic limit of the energy conversion efficiency that can be obtained in near-field thermal radiation.