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Thermal conductance of single-molecule junctions

Single-molecule junctions have been extensively used to probe properties as diverse as electrical conduction^1,2,3, light emission⁴, thermoelectric energy conversion^5,6, quantum interference^7,8, heat dissipation^9,10 and electronic noise¹¹ at atomic and molecular scales. However, a key quantity of current interest—the thermal conductance of single-molecule junctions—has not yet been directly experimentally determined, owing to the challenge of detecting minute heat currents at the picowatt level. Here we show that picowatt-resolution scanning probes previously developed to study the thermal conductance of single-metal-atom junctions¹², when used in conjunction with a time-averaging measurement scheme to increase the signal-to-noise ratio, also allow quantification of the much lower thermal conductance of single-molecule junctions. Our experiments on prototypical Au–alkanedithiol–Au junctions containing two to ten carbon atoms confirm that thermal conductance is to a first approximation independent of molecular length, consistent with detailed ab initio simulations. We anticipate that our approach will enable systematic exploration of thermal transport in many other one-dimensional systems, such as short molecules and polymer chains, for which computational predictions of thermal conductance^13,14,15,16 have remained experimentally inaccessible.

L. Cui, S. Hur, Z. A. Akbar, J. C. Klöckner, W. Jeong, F. Pauly, S.-Y. Jang, P. Reddy, and E. Meyhofer
Nature 572, 628–633 (2019)
DOI: 10.1038/s41586-019-1420-z