Thermal conduction and interface effects in nanoscale Fermi-Pasta-Ulam conductors

We perform classical non-equilibrium molecular dynamics simulations to calculate heat flow through a microscopic junction connecting two larger reservoirs. In contrast to earlier works, we also include the reservoirs in the simulated region to study the effect of the bulk-nanostructure interfaces and the bulk conductance. The scalar Fermi--Pasta--Ulam (FPU) model is used to describe the effects of anharmonic interactions in a simple manner. The temperature profile close to the junction in the low temperature limit is shown to exhibit strong directional features that fade out when temperature increases. Simulating both the FPU chain and the two bulk regions is also shown to eliminate the non-monotous temperature variations found for simpler geometries and models. We show that with sufficiently large reservoirs, the temperature profile in the chain does not depend on the details of thermalization used at the boundaries.