New Research Offers Hope for Room-Temperature Superconductivity

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Levitating trains, ultra-efficient energy storage, and quantum computers: superconductivity could unlock a wealth of possibilities for the future. But there is one major obstacle: most superconductors only work at extremely low temperatures, making practical, large-scale applications difficult and expensive. New research led by scientists from LMU Munich, Utrecht University, and Leiden University has now shed light on one of the key requirements for achieving superconductivity at room temperature. Their findings, published today in the leading journal Science, bring scientists a step closer to understanding how this might be achieved.

When you turn on a toaster, electricity flows through a metal wire. The wire heats up until it glows red-hot, toasting your bread. This happens because the wire resists the flow of electric current, converting electrical energy into heat.

That is exactly what you want in a toaster. But for most other applications, resistance is undesirable. For example, when you want to charge your phone, resistance causes valuable energy to be lost.

Extremely low temperatures

Superconductivity offers a way around this problem. It is a physical phenomenon in which certain materials conduct electricity without any resistance. The catch? Most superconductors only work at extremely low temperatures. For many materials, this means cooling them to around -260°C using liquid helium. This is an energy-intensive and expensive process.

Early discoveries

Scientists first discovered superconductivity in 1911. In the mid-1980s, they made another breakthrough: the discovery of materials that become superconducting at considerably higher temperatures, although these temperatures were still around -173°C.

There was a problem, however. The theory that explains conventional, low-temperature superconductivity could not account for this new type of superconductivity. And scientists still do not understand how it works.

“Understanding superconductivity in these materials is one of the grand unsolved problems of physics,” says Milan Allan, Chair of Experimental Physics - Quantum Metrology and Sensing and one of the research leaders. “And if you don’t understand it, you can’t improve the materials for technology.”

New potential route

The new research has helped the team, also including people from Leiden, Utrecht, Brookhaven, unravel part of this mystery. Their findings provide new insight into how high-temperature superconductivity works. Jiasen Niu, a postdoc from LMU and one of the lead authors, thinks that this offers new hope for superconductivity at higher temperatures: “We now identified what we the obstacles for higher-temperature superconductivity are”.

Dancing pairs

The two key ingredients for superconductivity are the formation of electron pairs, known as Cooper pairs, and the ability of these pairs to move synchronously. Imagine ten couples on a dance floor: it is not enough for each couple to dance together; they must also move in step with one another.

In conventional, low-temperature superconductors, electron pairing and this collective coordination occur together. The new research indicates that this is not the case in high-temperature superconductors. In these materials, electrons seem to already form pairs at temperatures well above the point at which superconductivity sets in. So why is superconductivity not happening at these higher temperatures? At the Allan lab at LMU, this is a focus of current research.

New measuring equipment

The research was made possible by new measuring equipment, developed and built by the researchers themselves. “The beauty of building new instruments is that you can measure things that nobody else can measure, you can gain insights that were invisible before”, says Maialen Ortego Larrazabal, who built important parts of the instrument during her PhD. It is this instrument that allowed them to distinguish between electrical current carried by individual electrons and current carried by electron pairs. This gave the team a way to investigate when and how electron pairing occurs in the material.