Quantized heat conduction by photons observed

November 9, 2006

In a recent experiment, published in Nature on November 9, Dr Matthias Meschke and professor Jukka Pekola from Helsinki University of Technology (Finland), together with Dr Wiebke Guichard from French CNRS, investigated heat exchange between two small pieces of normal metal, connected to each other only via superconducting leads. The results demonstrate that at very low temperatures heat is transferred by electromagnetic radiation.

The researchers are interested in how heat is transported in nano- and micrometer sized devices on an ordinary silicon chip at only 0.1 degrees above absolute zero.

Generally, even experts consider that superconductors are ideal insulators as regards to usual heat conduction. These new experimental results demonstrate that at very low temperatures heat is transferred by electromagnetic radiation, much in analogy to how light is propagated, along the superconductors, and furthermore these observations show that the heat transfer rate cannot have an arbitrary value: it is limited by what is called a quantum of thermal conductance. As is often the case, this observation contradicts our experiences in daily life. Certainly, one would not see this effect for instance while cooking an egg; it is just another example of how physical laws are changing when quantum mechanics comes into play.

These experiments are quite demanding, as they have to measure the temperature of an extremely tiny piece of a metal. Any usual thermometer would not do it, as it is simply far too big. Again, only the quantum mechanics can provide a solution: nano-sized (about 100 nm in cross-section) probes make use of the quantum mechanical effect of tunneling, that is penetration of particles through a classically forbidden area. Electrical current due to tunneling probes the energy distribution, and thus temperature, of the electrons in the metal. The experiment may have seemed too easy, unless, in order to distinguish the signal from the background, the researchers had to install an “in-situ” switch into the superconducting line: this allowed them to alternatively either pass or reject the heat by electromagnetic radiation through it.

The observation demonstrates a very basic phenomenon, which has no immediate consequences for new products or applications. Yet the observation helps us to understand the fundamental transport mechanisms in nanoscale devices. This effect has implications for, e.g., performance and design of ultra-sensitive radiation detectors in astronomy, whose operation at very low temperature is largely dependent on weak thermal coupling between the device and its environment.

Citation: Matthias Meschke, Wiebke Guichard and Jukka P. Pekola, Single-mode heat conduction by photons. Nature November 9th, 2006.

Source: Academy of Finland

Explore further: UQ, partners taking computing out of this world

Related Stories

A one-two punch hits pancreatic cancer where it hurts

April 5, 2017

Australian scientists have uncovered a promising new approach to treating pancreatic cancer, by targeting the tissue around the tumour to make it 'softer' and more responsive to chemotherapy. The findings are published today ...

Powering lasers through heat

November 13, 2012

In micro electronics heat often causes problems and engineers have to put a lot of technical effort into cooling, for example micro chips, to dissipate heat that is generated during operation. Austrian physicists have now ...

Recommended for you

Quantum thermometer or optical refrigerator?

June 22, 2017

In an arranged marriage of optics and mechanics, physicists have created microscopic structural beams that have a variety of powerful uses when light strikes them. Able to operate in ordinary, room-temperature environments, ...

A 100-year-old physics problem has been solved

June 22, 2017

At EPFL, researchers challenge a fundamental law and discover that more electromagnetic energy can be stored in wave-guiding systems than previously thought. The discovery has implications in telecommunications. Working around ...

Ultra-thin camera creates images without lenses

June 22, 2017

Traditional cameras—even those on the thinnest of cell phones—cannot be truly flat due to their optics: lenses that require a certain shape and size in order to function. At Caltech, engineers have developed a new camera ...

Problem of wheeled suitcases wobbling explained

June 21, 2017

(Phys.org)—A team of researchers at Universite Paris-Diderot has uncovered the reason for wobbling of wheeled suitcases. In their paper published in Proceedings of the Royal Society A, the group explains the physics behind ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.