Ames National Laboratory scientists have discovered miazite, a natural mineral that is an unusual superconductor, challenging previous beliefs and improving our understanding of superconductivity for future technologies.

Scientists at Ames National Laboratory have identified the first unusual superconductor whose chemical composition is also found in nature. Miasite is one of four naturally occurring minerals that act as superconductors when grown in the laboratory.

The team’s study of miazite showed that it is an unusual superconductor with properties similar to high-temperature superconductors. Their findings improve scientists’ understanding of this type of superconductivity, which could lead to more sustainable and cost-effective superconductor-based technology in the future.

Understanding Superconductivity

superconductivity The ability of the material to conduct electricity without losing energy. Superconductors find applications including medical MRI machines, power cables, and quantum computers. Conventional superconductors are well researched 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 unusual superconductors, many of which had much higher critical temperatures. According to Ames Laboratory scientist Ruslan Prozorov, all these materials are grown in the laboratory. This fact has led to the general opinion that unusual superconductivity is not a natural phenomenon.

a natural phenomenon

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, such as oxygen. Myyazit (Rh ₁₇ S ₁₅ ) is an interesting mineral for several reasons; one of which is its complex chemical formula. “Intuitively you think that this is something that was produced on purpose during a purposeful search and cannot exist in nature,” Prozorov said, “but it turns out that it is.”

Paul Canfield, professor emeritus of physics and astronomy at Iowa State University and scientist in the Ames laboratory, has expertise in the design, discovery, growth and characterization of new crystalline materials. He synthesized high-quality miazite crystals for this project. “Although miazite is a mineral discovered near the Miass River in Chelyabinsk Oblast, Russia, it is a rare mineral that does not generally grow into well-formed crystals,” Canfield said.

Growing myasite crystals was part of a larger effort to discover compounds combining very high melting point elements (such as Rh) and volatile elements (such as S). “We are mastering the use of mixtures of these elements that allow crystal growth at low temperature with minimal vapor pressure, unlike the nature of pure elements,” Canfield said. “It’s like finding a secret fishing hole full of big oily fish. We discovered three new superconductors in the Rh-S system. “Thanks to Ruslan’s detailed measurements, we discovered that miazite is an unusual superconductor.”

Advanced methods and findings

Prozorov’s group specializes in advanced methods for investigating superconductors at low temperatures. He said the material had to be 50 millielvin cold, which is about -460 degrees Fahrenheit.

Prozorov’s team used three different tests to determine the nature of miassite’s superconductivity. The main test is called “London Penetration Depth”. It determines how weakly the magnetic field can penetrate the volume of the superconductor from the surface. In a conventional superconductor this length is essentially constant at low temperature. However, in unconventional superconductors it varies linearly with temperature. This test showed that myasite behaves like an unusual superconductor.

Another test the team performed was adding defects to the material. Prozorov said the test is a special technique his team has been using for the past decade. It involves bombarding the material with high-energy electrons. This process creates defects in the crystal structure by removing ions from their positions. This disorder can cause changes in the critical temperature of the material.

Conventional superconductors are insensitive to nonmagnetic perturbation, so this test will show little or no change in critical temperature. Unconventional superconductors are highly sensitive to disorder, and the introduction of defects changes or suppresses the critical temperature. This also affects the critical magnetic field of the material. At Miacity, the team found that both the critical temperature and the critical magnetic field behave as predicted in unusual superconductors.

The study of unusual superconductors is improving scientists’ understanding of how they work. Prozorov explained that this is important because “uncovering unusual superconductivity mechanisms is the key to an economically justified application of superconductors.”