Simulation of nonequilibrium heat conduction in benzene single-molecule junctions

Problems of heat transport are ubiquitous to various technologies such as power generation, cooling, and thermoelectrics. In particular, the increased heat generated due to the miniaturization of electronic devices entails the degradation of its semiconductor components. This problem has lead to the emergence of single-molecule electronics, where long-chain molecules attached to tiny electrodes are used to transport and switch electrons. Thus the related problem of thermal transport through molecular junctions (MJs) has received considerable theoretical and experimental attention. In this work we simulate, by means of classical nonequilibrium molecular dynamics, a single-molecule junction composed of either benzene or biphenyl molecules connected to gold or platinum leads. The obtained temperature profile, computed for various values of the thermal bias, indicates ballistic heat transport. Thermal conductivity of the MJs with platinum leads is greater than that of gold-lead ones for both benzene and biphenyl molecules. Furthermore, MJs with a benzene molecule have higher thermal conductivity values than those with a biphenyl molecule. The performed spectral analysis indicates that the aforementioned difference can be accounted for by the increased presence of low-frequency modes in the spectra of the platinum MJ compared to the corresponding gold one, as well as by the absence of sulfur atoms in the former.