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nanotimes News in Brief

For many years, scientists at the Johannes Guten- berg University Mainz (JGU) in Germany have been world leaders in research on Heusler com- pounds, which are an important material class for the use in spintronic applications. Over the past few years, new application areas have emerged in the field of renewable energy, such as solar energy and thermoelectrics. And now Heusler compounds are also being considered for future technologies such as the quantum computer. “Calculations have un- covered a new quantum state of matter in Heusler compounds, which opens up previously unimagined usage possibilities,” explains Prof. Claudia Felser from Mainz University. “Heusler materials are real all-rounders and a veritable goldmine for futu- re technologies.” Together with Prof. Shoucheng Zhang of Stanford University, the scientist from Mainz has shown that many Heusler compounds can behave like topological insulators (TI). TIs were discovered just five years ago.

Key discoveries in the field of physics or material sciences are often made by chance during expe- riments in laboratories. However, this was not the case with topological insulators. In 2006, Prof. Zhang of Stanford predicted that a new quantum state of matter would be identified in nanostruc- tures of the familiar semiconductor mercury cadmi- um telluride (HgTe). One year later, this was con- firmed in experiments carried out by the Würzburg team led by Prof. Laurens Molenkamp. Completely new mathematical concepts are required to under- stand the physical aspects of what has been disco- vered.

The news that Heusler materials are now being considered as possible topological insulators has

10-07/08 :: July/August 2010

met with excitement all over the world. “There are two reasons for this,” explains Prof. Felser. “On the one hand, this large material class with over 1,000 known representatives contains more than 50 com- pounds that bear the hallmark of TIs. And on the other hand, it is now possible to design completely new physical effects. As the materials are made up of three elements, they can offer a range of other interesting features in addition to the topological quantum state.”

It is now possible to combine two quantum states such as superconductivity and topological surface effects. This paves the way for completely new and as yet undiscovered characteristics, some of which have already been predicted. “It was previously not considered possible to combine all these possibili- ties in just one material,” explains Prof. Felser.

Stanislav Chadov, Xiaoliang Qi, Jürgen Kübler, Gerhard H. Fecher, Claudia Felser & Shou Cheng Zhang: Tunable multifunctional topological insulators in ternary Heusler compounds, In: Nature Materials, Vol. 9(2010), No. 7, July 2010, Pages 541-545, DOI:10.1038/nmat2770: http://dx.doi.org/10.1038/nmat2770

Researchers at the Fraunhofer Institute for Mecha- nics of Materials IWM in Freiburg, Germany, are studying hydrogen-induced embrittlement. Their objective: to find materials and manufacturing processes that are compatible with hydrogen.

“With our new special laboratory, we are investi- gating how and at which speed hydrogen migrates through a metal. We are able to detect the points at which the element accumulates in the material, and

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