Kramers' theory frames chemical reaction rates in solution as reactants
overcoming a barrier in the presence of friction and noise. For weak coupling
to the solution, the reaction rate is limited by the rate at which the solution
can restore equilibrium after a subset of reactants have surmounted the barrier
to become products. For strong coupling, there are always sufficiently
energetic reactants. However, the solution returns many of the intermediate
states back to the reactants before the product fully forms. Here, we
demonstrate that the thermal conductance displays an analogous physical
response to the friction and noise that drive the heat current through a
material or structure. A crossover behavior emerges where the thermal
reservoirs dominate the conductance at the extremes and only in the
intermediate region are the intrinsic properties of the lattice manifest. Not
only does this shed new light on Kramers' classic turnover problem, this result
is significant for the design of devices for thermal management and other
applications, as well as the proper simulation of transport at the nanoscale.Comment: 8 pages, 5 figures. Supplementary Information available at the
journal publication or by request from the author
