Elementary physics in a single molecule

July 25, 2013

A team of physicists has succeeded in performing an extraordinary experiment: They demonstrated how magnetism that generally manifests itself by a force between two magnetized objects acts within a single molecule. This discovery is of high significance to fundamental research and provides scientists with a new tool to better understand magnetism as an elementary phenomenon of physics. The researchers published their results in the latest issue of Nature Nanotechnology.

The smallest unit of a magnet is the magnetic moment of a single atom or ion. If two of these magnetic moments are coupled, two options result: Either the magnetic moments add up to a stronger moment or they compensate each other and magnetism disappears. From the point of view, this is referred to as a triplet or singlet. A team of researchers around Professor Mario Ruben from Karlsruhe Institute of Technology and Professor Heiko B. Weber from the Friedrich-Alexander-Universität Erlangen-Nürnberg now wanted to find out whether the magnetism of a pair of magnetic moments can be measured electrically in a single molecule.

For this purpose, the team headed by Mario Ruben used a customized molecule of two for the experiment. At Erlangen, Heiko B. Weber and his team studied the molecule in a so-called single-molecule junction. This means that two metal electrodes are arranged very closely to each other, such that the molecule of about 2 nm in length is kept stable between these electrodes for many days, while current through the junction can be measured. This experimental setup was then exposed to various, down to very deep, temperatures.

The scientists found that magnetism can be measured in this way. The state in the molecule became visible as Kondo anomaly. This is an effect that makes electric resistance shrink towards deep temperatures. It occurs only when magnetism is active and, hence, may be used as evidence. At the same time, the researchers succeeded in switching this Kondo effect on and off via the applied voltage. A precise theoretical analysis by the group of Assistant Professor Karin Fink from Karlsruhe Institute of Technology determines the various complex quantum states of the cobalt ion pair in more detail. Hence, the researchers succeeded in reproducing elementary physics in a single molecule.

Explore further: Observation, electric current control of a local spin in a single-molecule magnet

More information: Nature Nanotechnology doi: 10.1038/nnano.2013.133

Related Stories

Nature: Electronic read-out of quantum bits

August 16, 2012

Quantum computers promise to reach computation speeds far beyond that of today's computers. As they would use quantum effects, however, they would also be susceptible to external interferences. Information flow into and out ...

Penetrating the quantum nature of magnetism

June 17, 2013

Antiferromagnets are materials that lose their apparent magnetic properties when cooled down close to absolute zero temperature. Different to conventional magnets, which can be described with classical physics even at the ...

The ferromagnetic Kondo effect

July 24, 2013

A group of physicists that includes scientists of the International School for Advanced Studies (SISSA) of Trieste have shown how to obtain a particular case of a physical effect – so far never observed in reality – whose ...

Recommended for you

New device converts DC electric field to terahertz radiation

August 4, 2015

Terahertz radiation, the no-man's land of the electromagnetic spectrum, has long stymied researchers. Optical technologies can finagle light in the shorter-wavelength visible and infrared range, while electromagnetic techniques ...

The resplendent inflexibility of the rainbow

August 4, 2015

Children often ask simple questions that make you wonder if you really understand your subject. An young acquaintance of mine named Collin wondered why the colors of the rainbow were always in the same order—red, orange, ...

Magnetism at nanoscale

August 3, 2015

As the demand grows for ever smaller, smarter electronics, so does the demand for understanding materials' behavior at ever smaller scales. Physicists at the U.S. Department of Energy's Ames Laboratory are building a unique ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

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.