How can we create the greatest superconductors that continue to be superconducting even at the highest temperatures and atmospheric pressures? is one of the most fascinating races in contemporary physics. With the discovery of nickelates in recent years, a new era of superconductivity has dawned. Since these superconductors are nickel-based, many scientists refer to the current period of superconductivity study as the “nickel age of superconductivity research.” Nickelates and cuprates, which were both discovered in the 1980s and are based on copper, are comparable in many ways.
However, a new class of materials is already in use thanks to a collaboration between TU Wien and Japanese universities that made it possible to more accurately model the behaviour of diverse materials on a computer than ever before.
Superconductivity has a “Goldilocks zone” where it performs best. And it is palladium, not nickel or copper, that is used to enter this zone. A new “age of palladates” in superconducting research may result from this. Now, the findings have been released in the publication Physical Review Letters.
Higher transition temperatures are being sought after
Superconductors act remarkably similarly to conventional conducting materials at high temperatures. However, when they are cooled below a specific critical temperature, a remarkable transformation occurs: their electrical resistance entirely vanishes, and all of a sudden, they are able to conduct electricity losslessly. The critical temperature is the point at which a material transitions from a superconducting to a typically conducting state.
“We have now been able to calculate this critical temperature for a whole range of materials. With our modeling on high-performance computers, we were able to predict the phase diagram of nickelate superconductivity with a high degree of accuracy, as the experiments then showed later,” says Prof. Karsten Held from the Institute of Solid State Physics at TU Wien.
While some materials only reach superconductivity at temperatures just over absolute zero (-273.15°C), others continue to exhibit these properties even at far higher temperatures. The way we produce, transport, and consume electricity would undergo a fundamental transformation if a superconductor could continue to be superconducting at normal ambient temperature and normal air pressure.
Such a substance hasn’t yet been found, though. Nevertheless, high-temperature superconductors, particularly those from the cuprate class, are crucial to technology. They can be used to transmit huge currents or generate incredibly powerful magnetic fields, for example.
palladium, copper or nickel?
Finding the optimum superconducting materials is challenging since there are so many different chemical components to consider. To maximise superconductivity, you can combine them in various ways and add minute traces of additional components. According to Prof. Karsten Held, “To find suitable candidates, you have to understand on a quantum-physical level how the electrons interact with one another in the material.”
This demonstrated that the strength of the electrons’ interactions has a maximum. The encounter ought to be potent but not overpowering. The highest transition temperatures are achievable because of a “golden zone” that exists between them.
Palladates as the best remedy
Neither cuprates nor nickelates are capable of achieving this ideal zone of medium contact, but a brand-new substance known as palladates can. In the periodic table, palladium is located directly one line below nickel. The qualities are comparable, but the electronic interaction is weaker because the electrons are, on average, farther away from the atomic nucleus and from one another, according to Karsten Held.
The model calculations show how to achieve optimal transition temperatures for palladium data. “The computational results are very promising,” says Karsten Held. “We hope that we can now use them to initiate experimental research. If we have a whole new, additional class of materials available with palladates to better understand superconductivity and to create even better superconductors, this could bring the entire research field forward.”
