Abstract
We present an analytical model and molecular-dynamics simulations of the phonon heat transport in nanowires and nanoribbons with anharmonic lattices and dynamically rough surfaces and edges. In agreement with recent experiments on heat transport in single-crystalline silicon nanowires with rough surfaces, our model and simulations predict finite and length-independent phonon thermal conductivity in such quasi–one-dimensional systems, in contrast to anomalous phonon thermal conductivity of corresponding momentum-conserving systems with atomically smooth surfaces, divergent with the system length. Within our model, the main cause of thermal conductivity reduction is the momentum-nonconserving scattering of longitudinal acoustic phonons by anharmonic side phonon leads in quasi–one-dimensional phonon waveguides with dynamically rough surface or edge layers. We also show that the superdiffusion of thermal energy in nanoribbons with atomically smooth edges is replaced by the normal diffusion or subdiffusion in nanoribbons with dynamically rough edges.