Room-temperature superconductors would revolutionize nearly every technology on Earth, but the path toward that “holy grail” of materials is a long one.
Scientists from Caltech might’ve just taken one step down that very path, with the discovery of a new superconducting state called Cooper-pair density modulation.
Although not a direct discovery of a room-temp superconductor, understanding the underlying mechanism of the state’s zero-electrical-resistance superpower is necessary for eventually finding that long-sought-after breakthrough.
Since their discovery by Dutch physicist Heike Kamerlingh Onnes in 1911, superconductors (materials with zero electrical resistance) have formed the foundation of some of the most groundbreaking technologies on the planet—from MRI machines to fusion reactors. However, superconductors come with one well-known limitation: they only exist near temperatures approaching absolute zero.
Progress in the ensuing century has slowly raised that temperature threshold—some copper oxides, for example, can be superconductors north of 130 Kelvin (or -225 degrees Fahrenheit). But these super-cold temperatures still limit the technology’s widespread adoption.
What the world really needs is a material that acts as a superconductor at room temperature (and, ideally, ambient pressure), but that’s easier said than done. In the past few years, scientists have made bold claims of finding these “holy grail” materials, but none of them have held up to scientific scrutiny. That doesn’t mean, however, that progress isn’t being made.
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A new paper published by an international team of scientists has found a new superconducting state known as Cooper-pair density modulation, or PDM. Although this breakthrough has not directly created room-temperature superconductors, it crucially deepens our knowledge about how superconductivity works and furthers our unending search for that wondrous material. The results of the study were published in the journalNature.
“Understanding the mechanisms leading to the formation of superconductivity and discovering exotic new superconducting phases is not only one of the most stimulating pursuits in the fundamental study of quantum materials but is also driven by this ultimate dream of achieving room-temperature superconductivity,” Stevan Nadj-Perge, the senior author of the study from Caltech, said in a press statement.
When superconductors reach their critical temperature (Tc), they form what are called Cooper pairs in conjunction with vibrations in the atomic crystalline structure known as phonons. If the metals stay within this narrow energy gap, the pairs do not lose energy due through collisions—a.k.a. superconductivity.
“These electrons pair up over distances that are larger than the scale at which they’d be hitting atoms,” Nadya Mason, a condensed matter physicist at the University of Illinois Urbana-Champaign,toldPopular Mechanicsback in 2023. “So if you imagine a road that has a lot of bumps in it, [electron pairs] lift themselves up above the road […] so that the bumps are irrelevant to them.”
However, this study further investigates the idea that this energy gap could vary across a material, meaning it would be stronger in some areas and weaker in others. This led to the development of an idea known as the pair density wave (PDW) in the 2000s, which suggests that this modulation occurs across a long wavelength.
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Now, this new research—working with an iron-based superconductor—has discovered the smallest possible wavelength modulation. In fact, it matches the space between atoms in the crystalline structure. They call this unexpected superconducting state Cooper-pair density modulation. The team made this discovery thanks to scanning tunneling microscopy, as well as a new technique that limited surface contamination for microscopic probling.
“The observed gap modulation, reaching up to 40 percent, represents the strongest reported so far, leading to the clearest experimental evidence to date that gap modulation can exist even at the atomic scale,” Lingyuan Kong, lead author of the new paper from Caltech, said in a press statement.
The team also reports that this PDM state likely exists beyond just the thin flakes of iron used in this study, and hopes that further investigation could give rise to “novel phenomena” in other materials. This likely doesn’t refer to room-temperature superconductors—or, at least, not yet—but a better understanding of the mechanism behind these wonder materials can help aid in that seemingly unending search.
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Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.