Mechanisms causing thermal rectification: The influence of phonon frequency, asymmetry, and nonlinear interactions

We have determined the mechanisms leading to thermal rectification by applying the nonequilibrium Green's function method to study thermal transport through a one-dimensional asymmetric lattice. Thermal rectification occurs in the presence of nonlinear interactions and a nonuniform phonon frequency distribution. We show that thermal rectification results from the contribution of high-frequency phonons; a thermal rectifier can thus be realized by filtering out high-frequency phonons in a single direction. Using these results, we present methods of increasing the level of rectification, and also discuss possible limitations on thermal rectifier performance.