Quantized thermal transport in single-atom junctions
16/02/17 19:56
What does determine the heat flow through a single atom? This is the ultimate question in the field of nanoscale energy transport and its answer is crucial to establish the fundamental laws that should describe the thermal transport in a variety of nanoelectronic devices. In the context of electrical circuits, the atomic scale was first reached with the advent of metallic atomic-size contacts and single-molecule junctions in the 1990s. These systems constitute the ultimate limit of miniaturization and have emerged as an ideal playground to investigate quantum effects related to charge and energy transport. Thus for instance, in recent years it has been shown that transport properties of metallic atomic-size contacts such as the electrical conductance, shot noise, thermopower, or Joule heating are completely dominated by quantum effects, even at room temperature. However, the experimental study of thermal conduction in these atomic-scale systems continues to be a formidable challenge and it has remained elusive to date in spite of its fundamental interest.
This basic open problem has now been resolved in our work published in Science in collaboration with the groups of Pramod Reddy and Edgar Meyhofer (University of Michigan) and Fabian Pauly and Peter Nielaba (University of Konstanz). In this work, our experimental colleagues made use of custom-designed picowatt-resolution calorimetric scanning probes to measure simultaneously the electrical and thermal conductance of gold and platinum atomic contacts all the way down to the single-atom level. The experiments reveal that the thermal conductance of gold single-atom junctions is quantized at room temperature in units of the universal thermal conductance quantum. They also show that the Wiedemann-Franz law relating thermal and electrical conductance is satisfied even in single-atom contacts, irrespective of the metal. On the other hand, we show that all these observations can be quantitatively explained within the Landauer picture for quantum coherent thermal transport. In particular, our calculations indicate that the observations described above are due to the fact that electrons dominate the thermal conductance in these metallic nanowires, and in the gold case electrons proceed ballistically through the contacts via fully open conduction channels.
The experimental techniques developed by our colleagues in the University of Michigan in this work will enable the study of thermal transport in atomic chains and molecular junctions, which is key to investigating numerous fundamental issues that have remained inaccessible despite great theoretical interest.
You can see a brief description of our work in the following video:
You can also read about this story in Spanish in the press release of the Universidad Autonoma de Madrid, in English in the press release of the University of Michigan, and in German in the press release of the University of Konstanz. See also article in nanotechweb.org.
This basic open problem has now been resolved in our work published in Science in collaboration with the groups of Pramod Reddy and Edgar Meyhofer (University of Michigan) and Fabian Pauly and Peter Nielaba (University of Konstanz). In this work, our experimental colleagues made use of custom-designed picowatt-resolution calorimetric scanning probes to measure simultaneously the electrical and thermal conductance of gold and platinum atomic contacts all the way down to the single-atom level. The experiments reveal that the thermal conductance of gold single-atom junctions is quantized at room temperature in units of the universal thermal conductance quantum. They also show that the Wiedemann-Franz law relating thermal and electrical conductance is satisfied even in single-atom contacts, irrespective of the metal. On the other hand, we show that all these observations can be quantitatively explained within the Landauer picture for quantum coherent thermal transport. In particular, our calculations indicate that the observations described above are due to the fact that electrons dominate the thermal conductance in these metallic nanowires, and in the gold case electrons proceed ballistically through the contacts via fully open conduction channels.
The experimental techniques developed by our colleagues in the University of Michigan in this work will enable the study of thermal transport in atomic chains and molecular junctions, which is key to investigating numerous fundamental issues that have remained inaccessible despite great theoretical interest.
You can see a brief description of our work in the following video:
You can also read about this story in Spanish in the press release of the Universidad Autonoma de Madrid, in English in the press release of the University of Michigan, and in German in the press release of the University of Konstanz. See also article in nanotechweb.org.
