Steps to superconductivity at room temperature

The prospect of superconductivity at room temperature took a small step forward with a recent discovery by a team of Penn State physicists and materials scientists.

The surprising discovery involved layering a two-dimensional material called molybdenum sulfide with another material called molybdenum carbide. Molybdenum carbide is a well-known superconductor: electrons can flow through the material without any resistance. Even the best metals, such as silver or copper, lose energy through heat. This loss makes long-distance transmission of electricity more expensive.

“Superconductivity occurs at very low temperatures, close to absolute zero or 0 Kelvin,” said Mauricio Terrones, corresponding author in an article in procedures of the National Academy of Sciences published this week. “The alpha phase of Moly carbide is superconducting at 4 Kelvin.”

By superimposing metastable phases of molybdenum carbide with molybdenum sulfide, superconductivity occurs at 6 Kelvin, a 50% increase. Although this is not remarkable in itself (other materials have been shown to be superconducting at temperatures as high as 150 Kelvin), it was still an unexpected phenomenon that heralds a new method of increasing superconductivity at higher temperatures in other superconducting materials.

The team used modeling techniques to understand how the effect was produced experimentally.

“Calculations using quantum mechanics implemented within functional density theory aided in the interpretation of experimental measurements to determine the structure of buried molybdenum carbide / molybdenum sulfide interfaces,” said Susan Sinnott, professor of science and engineering. of materials and head of the department. “This work is a good example of how the synthesis, characterization, and modeling of materials can come together to advance the discovery of new material systems with unique properties.”

According to Terrones, “it is a fundamental discovery, but nobody believed that it would work. We are observing a phenomenon that, as far as we know, has never been observed before.”

The team will continue to experiment with superconducting materials with the goal of one day finding combinations of materials that can transport energy through the network with zero resistance.