Anharmonic phonon flow through molecular-sized junctions

A general many-body nonequilibrium Green's function approach for interacting phonons is developed, and applied to study the thermal conductance of an anharmonic molecular junction between two solid surfaces. We investigate the dependence of the nanojunction's thermal conductance on temperature, force constants, and bond anharmonicity, and identify different parameter regimes. The calculation results display quantum mechanical effects that differ significantly from classical predictions. The anharmonic technique presented extends the scope of fully quantum mechanical Green's function calculations of phonon transport, which until now had been largely restricted to harmonic (or noninteracting phonon) systems. Thus it may provide a powerful tool for the study of lattice thermal conduction in nanoscale systems, such as point contacts, molecular contacts, and interfaces.