Quantized heat conduction by photons observed

Nov 09, 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: Could 'Jedi Putter' be the force golfers need?

add to favorites email to friend print save as pdf

Related Stories

Building BICEP2: A conversation with Jamie Bock

Mar 18, 2014

Caltech Professor of Physics Jamie Bock and his collaborators announced on March 17, 2014 that they have successfully measured a B-mode polarization signal in the cosmic microwave background (CMB) using the ...

A brake for spinning molecules

Mar 13, 2014

Chemical reactions taking place in outer space can now be more easily studied on Earth. An international team of researchers from the University of Aarhus in Denmark and the Max Planck Institute for Nuclear ...

Recommended for you

Could 'Jedi Putter' be the force golfers need?

Apr 18, 2014

Putting is arguably the most important skill in golf; in fact, it's been described as a game within a game. Now a team of Rice engineering students has devised a training putter that offers golfers audio, ...

Better thermal-imaging lens from waste sulfur

Apr 17, 2014

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...