Solid state chemistry has produced a large number of materials with properties not found in nature. For example, high-temperature superconductivity in copper-oxide compounds called cuprates is quite different from the superconductivity of naturally occurring metals and alloys and is often referred to as unusual. Unusual superconductivity has also been observed in other synthetic compounds such as iron-based and heavy-fermion superconductors. Physicists AIIMS National Laboratory They found convincing evidence of unusual superconductivity in synthetic samples of Rh17S15It is also found as a mineral in nature Myazide.
Miacite is one of only four naturally occurring minerals that act as a superconductor when grown in the laboratory, and is the only mineral so far known to exhibit unusual superconductivity in its pure synthetic form. Photo credit: Paul Canfield.
Superconductivity is when a material can conduct electricity without loss of energy.
Superconductors have applications including medical MRI machines, electrical cables, and quantum computers.
Conventional superconductors are better understood but have lower 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 have very high critical temperatures.
„All these materials are grown in the lab,” said Ames National Laboratory researcher Ruslan Prozorov.
„This fact has led to the general belief that unusual superconductivity is not a natural phenomenon.”
„Finding superconductors in nature is difficult because most superconducting elements and compounds react with other elements such as metals and oxygen.”
„Miacite is an interesting mineral for several reasons, one of which is its complex chemical formula.”
„Intuitively, you think it's something created on purpose during a focused search, and it can't be in nature. But it turns out it does.”
Growing miazite crystals was part of a larger effort to find compounds that combine very high-melting elements (such as Rh) and volatile elements (such as S).
„In contrast to the nature of the pure elements, we have mastered the use of mixtures of these elements that allow low-temperature growth of crystals with low vapor pressures,” said Paul Canfield, a physicist at Ames National Laboratory and Iowa State University. .
„It's like finding a hidden fishing hole full of big fat fish. We discovered three new superconductors in the Rh-S system.
„Also, through detailed measurements, we discovered that miazide is an unusual superconductor.”
The researchers used three different tests to determine the nature of miazide's superconductivity.
The main test is called the London Penetration Depth. This determines how far a weak magnetic field can penetrate the superconducting bulk from the surface.
In a typical superconductor, this length is essentially constant at low temperatures.
However, in unconventional superconductors, it varies linearly with temperature.
This experiment shows that miazide acts as an unusual superconductor.
Another experiment the team performed was introducing defects into the material.
„This experiment is a signature technique that his group has used over the past decade. It involves bombarding matter with high-energy electrons,” Dr. Prozorov said.
„This process knocks the ions out of their positions, creating defects in the crystal structure.”
„This disorder can cause changes in the critical temperature of matter.”
Conventional superconductors are not sensitive to non-magnetic disorder, so this test shows no change at the critical temperature.
Unconventional superconductors are highly sensitive to disorder, and introducing defects can alter or suppress the critical temperature. It also affects the material's critical magnetic field.
In meacite, the scientists found that both the critical temperature and the critical magnetic field behaved as predicted in unusual superconductors.
Investigating unusual superconductors improves scientists' understanding of how they work.
„This is important because finding the mechanisms behind the unusual superconductivity is crucial for economically sound applications of superconductors,” said Dr. Prozorov.
This discovery is a Paper In the journal Communication materials.
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H. Kim and many others. 2024. Nodal superconductivity in myazide Rh17S15. Common subject 5, 17; doi: 10.1038/s43246-024-00456-w
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