Scientists at Ames National Laboratory have discovered miassite, a naturally occurring mineral that is an unconventional superconductor, challenging previous beliefs and advancing our understanding of superconductivity for future technology.
Scientists from Ames National Laboratory have identified the first unconventional superconductor with a chemical composition also found in nature. Miassite is one of only four minerals found in nature that act as a superconductor when grown in the lab.
The team’s investigation of miassite revealed that it is an unconventional superconductor with properties similar to high-temperature superconductors. Their findings further scientists’ understanding of this type of superconductivity, which could lead to more sustainable and economical superconductor-based technology in the future.
Understanding Superconductivity
Superconductivity is when a material can conduct electricity without energy loss. Superconductors have applications including medical MRI machines, power cables, and quantum computers. Conventional superconductors are well understood but have low critical temperatures. The critical temperature is the highest temperature at which a material acts as a superconductor.
In the 1980s, scientists discovered unconventional superconductors, many of which have much higher critical temperatures. According to Ruslan Prozorov, a scientist at Ames Lab, all these materials are grown in the lab. This fact has led to the general belief that unconventional superconductivity is not a natural phenomenon.
Natural Occurrence
Prozorov explained that it is difficult to find superconductors in nature because most superconducting elements and compounds are metals and tend to react with other elements, like oxygen. He said that miassite (Rh17S15) is an interesting mineral for several reasons, one of which is its complex chemical formula. “Intuitively, you think that this is something which is produced deliberately during a focused search, and it cannot possibly exist in nature,” said Prozorov, “But it turns out it does.”
Paul Canfield, Distinguished Professor of Physics and Astronomy at Iowa State University and a scientist at Ames Lab, has expertise in design, discovery, growth, and characterization of novel crystalline materials. He synthesized high-quality miassite crystals for this project. “Although miassite is a mineral that was discovered near the Miass River in Chelyabinsk Oblast, Russia,” said Canfield, “it is a rare one that generally does not grow as well-formed crystals.”
Growing the miassite crystals was part of a larger effort to discover compounds that combine very high melting elements (like Rh) and volatile elements (like S). “Contrary to the nature of the pure elements, we have been mastering the use of mixtures of these elements that allow for low-temperature growth of crystals with minimal vapor pressure,” said Canfield. “It’s like finding a hidden fishing hole that is full of big fat fish. In the Rh-S system we discovered three new superconductors. And, through Ruslan’s detailed measurements, we discovered that the miassite is an unconventional superconductor.”
Advanced Techniques and Findings
Prozorov’s group specializes in advanced techniques to study superconductors at low temperatures. He said the material needed to be as cold as 50 millikelvins, which is about -460 degrees DOI: 10.1038/s43246-024-00456-w
This work was supported by the DOE Office of Science (Office of Basic Energy Sciences) and used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility.