Phononic heat transport in molecular junctions: quantum effects and vibrational mismatch

In this work, we employ the quantum self-consistent reservoir (QSCR) method, which is based on the generalized quantum Langevin equation, to calculate phononic thermal conduction in molecular junctions. The method emulates phonon inelastic scattering processes while taking into account quantum effects. Specifically, we simulate the thermal conductance of linear, one-dimensional molecules with 3-10 particles bridging harmonic solids, while taking into account effective molecular anharmonicity by using the QSCR method. The results display the expected behavior of thermal conductance in anharmonic chains, as a function of length, phonon scattering rate, as well as temperature, thus validating the computational scheme. Moreover, we examine the effects of vibrational mismatch at the contacts on the heat transfer characteristics, and reveal the dual role of vibrational anharmonicity: It enhances the resistance of the system due to inelastic scattering processes, but it can promote energy transport across a vibrational mismatch by enabling phonon up-and-down-conversion processes.M.Sc