Longji Cui1 Edgar Meyhofer1 Pramod Sangi Reddy1

1, University of Michigan, Ann Arbor, Michigan, United States

The study of thermal energy transport and conversion at the nanoscale is of fundamental interest, and holds great promise for the development of a variety of technologies, including heat management in nanoelectronics, thermoelectrics and thermophotovoltaics. Although much attention has been directed towards studying nanocale optical and electronic properties, thermal properties from the atomic to molecular scale has been barely explored due to experimental challenges. In my presentation I will describe a series of novel experimental techniques and how they we leveraged them to systematically answer how heat is conduct through atomic contacts, radiated across nanoscale gaps and converted to electricity in molecular junctions. To directly observed the fundamental limits of thermal heat conduction at the single atom limit.. Specifically, by employing custom-fabricated picowatt-heat-resolution calorimetric scanning probes, we observed quantized thermal transport at room temperature in metallic wires that are only single-atom wide and verified the validity the Wiedemann-Franz law down to the single atom limit [1]. We examined radiative heat transfer in angstrom and nanometer scale gaps and observed heat fluxes that are several orders of magnitude larger than the far-field heat fluxes predicted by Planck’s Black body limit [2-3]. Finally, we studied thermoelectric energy conversion of organic molecule junctions [4]. These findings set the stage for rational design of thermally-efficient nanoscale devices and are expected to enable future development of environmentally-friendly energy saving solutions.

[1] L. Cui et al. Science, 355, 1192 (2017).
[2] L. Cui et al. Nature Communications, 8, 14479 (2017).
[3] K. Kim et al. Nature, 528, 387 (2015).
[4] L. Cui et al. Journal of Chemical Physics, 146, 092201 (2017).