Uranium ditelluride, discovered in 2019, challenges conventional understanding of superconductivity by regaining zero electrical resistance at magnetic fields far beyond those where it initially loses it, a behavior researchers at ISTA are now able to explain. Researchers led by ISTA PhD student Valeska Zambra developed a new high-field measurement technique to dissect this puzzling phenomenon in the quantum material UTe2, and the method is already being adopted in laboratories worldwide. “It seems like each measurement on UTe2 uncovers another mystery,” says Kimberly Modic, assistant professor at ISTA. “Our work now presents evidence for the mechanism behind some of these mysteries.” Understanding UTe2, which reenters a superconducting state between 40 and 70 Tesla after losing it around 10 Tesla, could unlock new insights into unconventional superconductivity and future technologies.
UTe2: Unconventional Superconductivity and Reentrant Behavior
Researchers at ISTA have elucidated the mechanism behind this “reentrant superconductivity” using a newly developed method to probe the material’s behavior. The team, led by Kimberly Modic, assistant professor at ISTA, focused on understanding the conditions leading to this regained superconductivity. They employed pulsed field facilities to subject UTe2 samples to rapidly fluctuating magnetic fields, increasing to 60 Tesla and back within a tenth of a second. This allowed them to investigate whether magnetic fluctuations within the material could be responsible for the high-field superconductivity. This innovative approach revealed a region of large transverse magnetic susceptibility in UTe2, which the researchers believe acts as the “glue” binding the material’s electrons together and enabling superconductivity under such extreme conditions.
The technique’s precision is noteworthy; the team utilized samples smaller than a grain of sand and has expertise in fabricating defect-free material. “Measuring samples roughly the thickness of a human hair is especially challenging, but this is precisely what our group specializes in,” explains Modic. The success of this method is already extending beyond ISTA, with high-field laboratories worldwide adopting the technique for their own research. Researchers have contacted Valeska to collaborate on establishing this technique further at their facilities. Zambra and Modic emphasize that fully understanding these new states of matter is crucial before considering potential applications, drawing a parallel to the accidental discovery of superconductivity over a century ago, which ultimately led to the development of MRI technology. “We might be looking at a completely new type of superconductivity for which we have not yet imagined applications,” concludes Modic, “but it’s a mystery, and mysteries are worth pursuing.”
60 Tesla Pulsed Field Technique Measures UTe2 Magnetization
The search for novel superconducting materials continues to drive innovation in condensed matter physics, with unconventional superconductors like uranium ditelluride (UTe2) presenting particularly intriguing challenges. Discovered in 2019, UTe2 defies expectations by regaining superconductivity at magnetic fields exceeding 40 Tesla after initially losing it around 10 Tesla, a behavior demanding detailed investigation. Researchers at ISTA have recently developed a technique utilizing pulsed magnetic fields reaching 60 Tesla to probe this unusual phenomenon, and the method is already gaining traction in laboratories globally. This new approach doesn’t simply confirm existing theories; it actively seeks to understand the underlying mechanisms driving UTe2’s reentrant superconductivity, the reappearance of zero electrical resistance at extreme fields. “We devised a method that allows us to interrogate the sample under extreme magnetic fields by giving it a controlled wiggle,” explains Valeska Zambra, a PhD student and first author of the Nature Communications paper detailing the findings. The precision of this method is noteworthy, as it allows researchers to utilize samples smaller than a grain of sand, while also possessing expertise in fabricating defect-free material.
But the catch is that UTe 2 is not magnetic. So, at first glance, it’s not obvious why this material exhibits such a special superconducting state.
Transverse Magnetic Susceptibility Reveals Electron Pairing
Valeska Zambra, a PhD student at ISTA, is spearheading a novel approach to understanding the perplexing behavior of UTe2, a uranium-based superconductor discovered in 2019. Unlike conventional superconductors which lose their zero-resistance state in magnetic fields, UTe2 surprisingly regains superconductivity at fields exceeding 40 Tesla, a phenomenon that has challenged existing theoretical frameworks. Zambra’s work, detailed in a recent Nature Communications paper, centers on a newly refined measurement technique that probes the material’s magnetic properties under extreme conditions, offering insight into the mechanism driving this unusual re-entrant superconductivity. The ISTA team developed a method to measure transverse magnetic susceptibility, a property indicating how easily a material becomes magnetized when exposed to a field perpendicular to its current. By “shaking” the sample within a rapidly fluctuating magnetic field increasing to 60 Tesla and back within a tenth of a second, researchers could effectively analyze the magnetization and identify key characteristics.
This technique is particularly valuable because it allows for analysis of material fabricated to be defect-free, a significant advantage over methods limited to larger crystals. This discovery provides a potential explanation for the re-entrant superconductivity observed in UTe2, where the material transitions back into a zero-resistance state after initially losing it.
It seems like each measurement on UTe 2 uncovers yet another mystery. Our work now presents evidence for the mechanism behind some of these mysteries.
Kimberly Modic, assistant professor at the Institute of Science and Technology Austria (ISTA)
Miniaturized Sample Fabrication Enables High-Field Analysis
The ability to probe the quantum realm often hinges on the physical constraints of sample size; recent advances at ISTA demonstrate how shrinking materials to microscopic dimensions is unlocking new insights into exotic states of matter, specifically the puzzling behavior of the uranium-based superconductor UTe2. Zambra’s method involves mounting the minuscule UTe2 samples on a cantilever, essentially a microscopic “stick,” and subjecting them to rapidly fluctuating magnetic fields. This technique allows researchers to effectively “shake” the crystal, simulating changes in the magnetic field’s direction and revealing crucial information about the material’s internal magnetic state. The impact of this miniaturized approach extends beyond ISTA’s laboratories; high-field laboratories worldwide are already adopting the technique, recognizing its potential to unlock further secrets within complex quantum materials. ISTA’s expertise in fabricating defect-free samples, combined with the use of samples smaller than a grain of sand, is a significant advantage. Modic emphasizes that while potential applications remain distant, the pursuit of fundamental understanding is paramount.
Although other unconventional superconductors exist, UTe 2 makes the word ‘unconventional’ almost sound like an understatement.
