Are there materials that conduct electricity without resistance at normal room temperature? This is one of the big questions in modern physics. If such a material were found, there would be countless applications – from energy-saving electric motors to loss-free electricity transmission to Europe from solar power plants in the Sahara. However, the search for such materials has so far failed because it is not yet understood how this unconventional high-temperature superconductivity occurs.

Prof. Karsten Held (Institute of Solid State Physics, TU Wien, Vienna) now wants to change that. He has developed a new method called ‘dynamic vertex approximation’. This technique makes it possible to accurately describe the complex interaction of a large number of electrons – and it is precisely this interaction that is crucial for high-temperature superconductivity. In recent years, Karsten Held and his team have repeatedly demonstrated that this method can yield the answers to important questions in solid-state physics. In particular, he has been able to accurately predict superconductivity and other properties of the latest nickelate superconductors. He has now received an ERC Advanced Grant from the European Research Council (ERC), the most highly endowed grant in European research, to investigate the mechanism of high-temperature superconductivity and to find new, better superconductors.

High temperature, but still ice cold

So-called ‘high-temperature superconductors’ have been known for many decades – materials that retain their superconducting properties even at relatively high temperatures. However, these temperatures are still quite cold for human standards – typically, liquid nitrogen is used to cool them to -196°C. “A material that remains superconducting even at room temperature would completely change the way we generate, transport and consume electrical energy,” says Prof. Karsten Held.

It is extremely difficult to describe high-temperature superconductivity in theory. The problem is that the quantum physical interactions between the electrons must be described accurately. However, as the number of electrons involved increases, the equations of quantum theory quickly become so complex that even the world's best supercomputers cannot solve them. A better, more efficient method of calculating superconducting materials is therefore needed.

To this end, Karsten Held has developed a technique based on so-called ‘Feynman diagrams’ – these were actually developed for particle physics by Nobel Prize winner Richard Feynman. Using this approach, Karsten Held was able to predict with remarkable accuracy the conditions under which important high-temperature superconductors, known as nickelates, remain superconducting. The calculated energy levels of the electrons and the magnetic properties were also impressively confirmed by measurements last year.

“This puts us in the unique position of being able to perform realistic, material-specific calculations for novel nickelates, but also for cuprates and completely different, as yet unknown superconductors,” says Karsten Held. The new method can also be used to calculate how materials behave that are composed of nanometre-thin layers of different materials or in which very specific additional foreign atoms are added. “The goal is to better understand high-temperature superconductivity and to design new superconducting materials on the computer,” says Karsten Held.

Karsten Held

Karsten Held studied at RWTH Aachen University and obtained his doctorate in Augsburg in 1999. With an Alexander von Humboldt Fellowship, he then went to Princeton University as a postdoc; in 2002, he returned to Europe and headed an Emmy Noether group at the Max Planck Institute for Solid State Research in Stuttgart. In 2008, he was appointed professor at the Institute of Solid State Physics at TU Wien.

The ERC Advanced Grant, worth 2.1 million euros, will now give Karsten Held the opportunity to further expand his team at the highest international level and to advance research on high-temperature superconductivity over the next five years. This is already the second ERC grant awarded to Karsten Held: he received an ERC Starting Grant in 2012.

Rückfragehinweis

Prof. Karsten Held
Institut für Festkörperphysik
Technische Universität Wien
+43-1-58801-13710
karsten.held@tuwien.ac.at

Aussender:
Dr. Florian Aigner
Kommunikation
Technische Universität Wien
+43 664 60588 4127
florian.aigner@tuwien.ac.at