Thermal conductance of the Fermi-Pasta-Ulam chains: atomic to mesoscopic transition.

We demonstrate that in the atomic-scale limit the thermal conductance K of the Fermi-Pasta-Ulam (FPU) model and its variants strongly deviates from the mesoscopic behavior due to the relevance of contact resistance. As a result, atomic chains follow log K=nu log T, where the power-law coefficient nu is exactly two times larger than the mesoscopic value. We smoothly interconnect the atomic and mesoscopic limits and demonstrate that this turnover behavior takes place in other nonlinear FPU-like models. Our results are significant for nanoscale applications, manifesting an atomic thermal conductance with temperature scaling superior to the mesoscopic limit.