Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Heat transport through single molecules


International team of researchers with participation of the University of Konstanz achieves breakthrough in the area of heat transport at molecular scales

Combining novel theoretical and experimental approaches, researchers from the University of Michigan (USA), Kookmin University (South Korea), the University of Konstanz (Germany) and the Okinawa Institute of Science and Technology Graduate University (Japan) have successfully measured and described the thermal conductance of single-molecule junctions – a key quantity in nanoscale transport phenomena that has so far eluded direct experimental determination. A joint paper entitled “Thermal Conductance of Single-Molecule Junctions” has been published online in the journal Nature on 17 July 2019.

Illustration of the experimental setup to measure the heat flow through a single molecule.

Copyright: Jan C. Klöckner

“The control of heat transport at the molecular scale is a key factor in the development of nanostructured materials and technologies such as molecular electronics, thermally conductive polymers and thermoelectric energy-conversion devices”, explains Associate Professor Fabian Pauly, a theoretical condensed matter physicist and the leader of the Quantum Transport and Electronic Structure Theory Unit at Okinawa Institute of Science and Technology Graduate University.

Fabian Pauly, who is also a Principal Investigator at the University of Konstanz’s Collaborative Research Centre 767 “Controlled Nanosystems: Interaction and Interfacing to the Macroscale”, contributed the theoretical models to the experimental breakthrough.

In short molecules, thermal energy transfer is believed to be determined by phase-coherent, ballistic processes as compared to incoherent and diffusive ones in conventional macroscopic systems.

“The problem is that while a range of other single-molecule-level transport properties have been successfully measured in the past, thermal conductance has proven difficult to determine due to considerable challenges associated with detecting extremely small heat currents at picowatt resolution”, Fabian Pauly continues.

Experimental breakthrough

Scientists from the Department of Mechanical Engineering at the University of Michigan managed to successfully measure thermal transport through single-molecule junctions for the very first time. They applied a custom-developed calorimetric-scanning-thermal-microscopy technique to prototypical thiol-terminated alkane molecules which were provided by researchers from the Department of Chemistry at Kookmin University in South Korea.

Working in an ultra-high vacuum environment, the US team used a self-assembled monolayer of alkane molecules to facilitate the formation of single-molecule junctions between a gold-coated microscope tip and a gold substrate.

The transfer of heat from the heated tip to the cold substrate, which was kept at room temperature throughout, allowed the researchers to determine the resulting thermal conductance, which was found to originate from the vibrations of atoms, also called phonons. A sophisticated averaging technique was required to measure the small quantity.

The theory behind the experiments

As Fabian Pauly points out: “Previous theoretical work conducted in my group made predictions on the size of thermal conductance values for various single-molecule junctions, providing important information to our experimental colleagues regarding the measurement resolution required to achieve successful quantification”.

Combining nonequilibrium Green’s function techniques with density functional theory in custom-developed code, Fabian Pauly and his doctoral student Jan Klöckner, who is based at University of Konstanz, were able to compute the thermal conductance due to phonons for junction geometries containing alkane molecules of variable length.

The experiments with such molecules that were conducted at the University of Michigan yield strong experimental evidence in support of the theorists’ assumptions of a phase-coherent transport regime. “In other words, heat transport in alkane-based single-molecule junctions is virtually independent of length”, explains Jan Klöckner, who helped to develop the ab initio simulations used to understand the experimental data.

These insights do not only resolve the longstanding problem of determining thermal conductance at the single-molecule level experimentally. They will also enable systematic studies of thermal transport through other one-dimensional systems such as polymer chains: “Having shown that heat transport at the molecular scale is length-independent, we must now try to find out how we can enhance or reduce it. Ultimately, what we hope to do in the future is to identify ways of controlling the flow of heat by molecular design”, concludes Fabian Pauly.

- Original publication: Longji Cui, Sunghoon Hur, Zico Alaia Akbar, Jan C. Klöckner, Wonho Jeong, Fabian Pauly, Sung-Yeon Jang, Pramod Reddy, Edgar Meyhofer. Thermal Conductance of Single-Molecule Junctions. Nature, 17.07.2019. DOI:
- Researchers from the University of Michigan (USA), Kookmin University (South Korea), the University of Konstanz (Germany) and the Okinawa Institute of Science and Technology Graduate University (Japan) have successfully measured and described the thermal conductance of single-molecule junctions for the first time
- Groundbreaking experiments, conducted at the University of Michigan, pave way for further research into thermal transport through single molecules and other one-dimensional systems
- Theoretical models developed by Fabian Pauly (University of Konstanz and Okinawa
Institute of Science and Technology Graduate University) and Jan Klöckner (University of Konstanz)
- Fabian Pauly’s and Jan Klöckner’s research supported by the University of Konstanz’s Collaborative Research Centre 767 “Controlled Nanosystems: Interaction and Interfacing to the Macroscale”

Note to editors:
An image is available for download here:
Caption: Illustration of the experimental setup to measure the heat flow through a single molecule. A heated tip of a scanning tunneling microscope (STM) is brought close to a cold substrate so that a single molecule can bridge the gap between them.
Copyright: Jan C. Klöckner

University of Konstanz
Communications and Marketing
Phone: + 49 7531 88-3603

Julia Wandt | idw - Informationsdienst Wissenschaft

More articles from Physics and Astronomy:

nachricht Explained: Why water droplets 'bounce off the walls'
27.02.2020 | University of Warwick

nachricht Scientists 'film' a quantum measurement
26.02.2020 | Stockholm University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: High-pressure scientists in Bayreuth discover promising material for information technology

Researchers at the University of Bayreuth have discovered an unusual material: When cooled down to two degrees Celsius, its crystal structure and electronic properties change abruptly and significantly. In this new state, the distances between iron atoms can be tailored with the help of light beams. This opens up intriguing possibilities for application in the field of information technology. The scientists have presented their discovery in the journal "Angewandte Chemie - International Edition". The new findings are the result of close cooperation with partnering facilities in Augsburg, Dresden, Hamburg, and Moscow.

The material is an unusual form of iron oxide with the formula Fe₅O₆. The researchers produced it at a pressure of 15 gigapascals in a high-pressure laboratory...

Im Focus: From China to the South Pole: Joining forces to solve the neutrino mass puzzle

Study by Mainz physicists indicates that the next generation of neutrino experiments may well find the answer to one of the most pressing issues in neutrino physics

Among the most exciting challenges in modern physics is the identification of the neutrino mass ordering. Physicists from the Cluster of Excellence PRISMA+ at...

Im Focus: Therapies without drugs

Fraunhofer researchers are investigating the potential of microimplants to stimulate nerve cells and treat chronic conditions like asthma, diabetes, or Parkinson’s disease. Find out what makes this form of treatment so appealing and which challenges the researchers still have to master.

A study by the Robert Koch Institute has found that one in four women will suffer from weak bladders at some point in their lives. Treatments of this condition...

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

Latest News

Preserved and fresh – Neutrons show details of the freeze drying process

27.02.2020 | Life Sciences

Underwater Snail-o-Bot gets kick from light

27.02.2020 | Health and Medicine

Explained: Why water droplets 'bounce off the walls'

27.02.2020 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>