Probing thermal transport in single-molecule junctions

Charge and energy transport in single-molecule junctions is of great interest to reveal exotic quantum transport phenomena at the fundamental size limit, and with potential applications in nanoelectronics and nanophotonics. A key quantity—the thermal conductance of single-molecule junctions—has eluded experimental determination due to challenges in detecting extremely small picowatt-level heat currents that occur in such systems. Here, by employing custom-developed scanning thermal microscopy (SThM) probes that enable picowatt-resolution, we report the quantitative measurement of the thermal conductance of single-molecule junctions and investigate the dependence of thermal transport on molecular length. Our experiments were performed on prototypical Alkanedithiol molecules, revealing that the thermal conductance is approximately independent of the molecular length and is consistent with ab initio simulations. The techniques presented here represent a breakthrough that will enable further studies of thermal transport in many other 1D organic systems, short molecules and polymers, for which interesting thermal transport properties have been theoretically predicted but remain experimentally inaccessible.
Reference: L. Cui et al., Nature 572, 628–633 (2019).