Image of the Month

February 2020

Thermal conductance of single-molecule junction is quantified by recording the temperature change of the Pt heater-thermometer when a single molecule junction is broken.

Fig. 1 | Experimental set-up and strategy for quantifying heat transport in single-molecule junctions.

Single-molecule junctions have been extensively used to probe properties as diverse as electrical conduction1–3, light emission4, thermoelectric energy conversion5,6, quantum interference7,8, heat dissipation9,10 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 conductance13–16 have remained experimentally inaccessible.

Nature 572, 628 – 633 (2019)

Longji Cui1,6, Sunghoon Hur1, Zico Alaia Akbar2, Jan C. Klöckner3,4, Wonho Jeong1, Fabian Pauly3,4*, Sung-Yeon Jang2,7*, Pramod Reddy1,5* & Edgar Meyhofer1*

1 Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
2 Department of Chemistry, Kookmin University, Seoul, South Korea.
3 Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan.
4 Department of Physics, University of Konstanz, Konstanz, Germany.
5 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
6 Present address: Smalley-Curl Institute and Department of Physics and Astronomy, Rice University, Houston, TX, USA.
7 Present address: Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea.

*e-mail: [email protected]; [email protected]; [email protected]; [email protected]

UHV Beetle 750 AFM-STM