TU Wien performed calculations involving the use of the precious metal palladium as a Goldilocks material to create superconductors that remain superconducting even at relatively high temperatures. Research continues in the field of modern physics: determining the optimal method for creating superconductors that retain their superconductivity at high temperatures and ambient pressure. Recently, this quest has been revived thanks to the advent of nickelates, ushering in a new era of superconductivity.

The basis for these superconductors is nickel, which has led many scientists to refer to this period of superconductivity research as the “Nickel Age”. In many respects, nickelates are similar to cuprates discovered in the 1980s based on copper.

But now a new class of materials comes into play: With a collaboration between TU Wien and universities in Japan, it has become possible to simulate the behavior of various materials on a computer with greater precision than before. There is a “Goldilocks region” where superconductivity works particularly well. And neither nickel nor copper reaches this region, but palladium. This could usher in a new “paladat age” in superconductivity research. The results were published in a scientific journal Physical Review Letters.

Look for higher transition temperatures

At high temperatures, superconductors behave very similarly to other conductive materials. But when they cool below a certain “critical temperature” they change dramatically: their electrical resistance completely disappears and they can suddenly conduct electricity without any loss. This limit, where the material alternates between superconducting and normally conducting states, is called the “critical temperature”.

“We have now been able to calculate this ‘critical temperature’ for a range of materials. Professor Carsten Held of the Institute for Solid State Physics at the University of Vienna said: “Thanks to our simulations on high-performance computers, we were able to predict with a high degree of accuracy the phase diagram of nickel superconductivity, as subsequent experiments have shown. ” says. .

Many materials become superconducting only slightly above absolute zero (-273.15°C), while others retain their superconducting properties even at much higher temperatures. A superconductor that is still superconducting at normal room temperature and normal atmospheric pressure will fundamentally change the way electricity is produced, transported and used. However, such material has not yet been found.

However, high-temperature superconductors, including those of the cuprate class, play an important role in technology – for example, in conducting large currents or creating extremely strong magnetic fields.

Copper? Nickel? Or Palladium?

Searching for the best possible superconducting materials is complex: there are many different chemical elements that are questionable. You can combine them into different structures, adding small traces of other elements to optimize superconductivity. “To find suitable candidates, you need to understand at a quantum-physical level how electrons interact with each other in the material,” says Professor Carsten Held. This indicated an optimum strength of electron interaction. The interaction should be strong, but not too strong. Between them there is a “golden zone” that allows you to reach the highest transition temperatures.

Paladati as the optimal solution

This gold zone of middle interaction cannot be reached with cuprates or nickelates – but can be hit with a new type of material, paladats. “Paladium is just one row below nickel on the periodic table. The properties are similar, but the electrons are, on average, slightly further away from the atomic nucleus and from each other, so the electronic interaction is weaker,” says Carsten Held.

Model calculations show how to reach optimum transition temperatures for palladium data. “The computational results are very promising,” says Carsten Held. “We now hope we can use them to begin experimental research. If we have an entirely new, additional class of materials introduced with paladats to better understand superconductivity and create even better superconductors, it can move the entire field of research forward.”