Research: Superconducting material discovered with unique code

Five years ago Peter Oppeneer, a professor of materials theory at the Department of Physics and Astronomy at Ångström Laboratory, decided to focus his attention on superconductors. At the time, no scientific tools were available to predict whether a material would become superconducting and, if so, at what temperature it would occur. Working at the Ångström Laboratory with Alex Aperis, a researcher in materials theory, Oppeneer and others started developing “Uppsala superconductivity code” – the code that researchers now have demonstrated can be used for just such predictions. This applies both to conducting research on existing materials and designing new ones.

“What fascinates me is that we can now understand things with incredible precision. Our understanding of superconductors becomes much deeper and broader. We acquire a lot of information we could not obtain before,” says Oppeneer.

“Yes, exactly, now we can look at a material and at the atomic level determine what is happening instead of relying on models,” says Alex Aperis.

Opens new doors for research

Both researchers find it very intriguing to have found a new way to investigate superconductivity.

“This is really interesting. It’s like opening the door to a new room or receiving whole new glasses,” says Aperis.

The material designed by the researchers is called hydrogenated magnesium diboride, MgB₂H, which was developed together with colleagues at the University of Antwerp. So far it does not exist as physical matter, but rather as a description created with the unique code. One of the things that surprised the researchers the most is that the material becomes superconducting at a relatively high temperature even though it is only three atoms thick. In this case that means a temperature of 67–100 Kelvin, which is the same as between minus 206 and minus 173 degrees Celsius.

High-temperature superconductors is the field were the world’s researchers currently are competing most intensively, says Peter Oppeneer. The ultimate dream is a material that becomes superconducting at room temperature, so that cooling becomes superfluous.

“Much of the research available is theoretically interesting but lacks practical applications. We think that the knowledge we gain through basic research can also be of interest to those conducting research focused on applications,” Oppeneer explains.

Use in MRI scanners and wind power

Today superconductors are used mainly to create very strong electromagnets used in magnetic resonance imaging scanners and particle accelerators, but also in areas such as wind power. The crux of the matter for large-scale and wide use is still finding materials that are superconducting at higher temperatures under normal pressure and that also have the correct mechanical properties. We are still awaiting breakthroughs in many possible applications, which could mean that it would become commonplace to have very efficient electric motors, super-fast computers no bigger than coins and power lines without electrical losses.

In their further work, Peter Oppeneer and Alex Aperis will primarily focus on using the code they have developed to try to understand the mechanisms behind what are called unconventional superconductors. These are superconducting materials for which no explanatory models currently exist.

“Now that we can investigate materials in a whole new way, we also see great opportunities for new discoveries,” says Oppeneer.

Facts

In order for superconducting to occur, a substantial cooling is usually required. High-temperature superconductors are materials that become superconducting at temperatures above 77 degrees Kelvin, or –196 degrees Celsius, and this allows them to be cooled with liquid nitrogen. When superconductivity was first discovered at the beginning of the 20th century, mercury was cooled down to 4.2 kelvins, or –273 degrees Celsius. Temperatures this low require liquid helium. Since it is much easier and cheaper to cool with nitrogen, the discovery of high-temperature superconductors represented something of a revolution in physics. This led to the Nobel Prize in Physics in 1987.

Publication

The research is published in Physical Review Letters, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.077001

Lisa Thorsén