Israeli discovery opens new paths for superconducting technologies
Baku, July 16, AZERTAC
Israeli scientists have discovered that two widely studied ultrathin superconducting materials are more complex than previously understood, according to TPS-IL. The findings address a long-standing question in superconductivity research and could help scientists better understand how to design future superconducting technologies, including quantum computers, ultra-efficient electronics and advanced sensors.
Researchers at The Hebrew University of Jerusalem found that materials long believed to behave as simple superconductors with a single energy gap actually contain two interacting superconducting states that combine so closely they appear as one.
The study was led by doctoral student Shahar Simon and master’s student Maya Klang under the guidance of Prof. Oded Millo and Prof. Hadar Steinberg of Hebrew University’s Racah Institute of Physics and the Center for Nanoscience and Nanotechnology. After completing her master’s degree, Klang moved to Switzerland to pursue a Ph.D at ETH Zurich.
Simon told The Press Service of Israel that the finding was especially surprising because niobium diselenide (NbSe2), the material at the center of the research, had been studied for decades and was considered a relatively simple superconducting system.
“I think what’s most interesting about it is that NbSe2 has been around for a while. It is an extremely popular 2D superconductor to research, and it has always been considered as having only a single state at the thin limit,” Simon explained to TPS-IL. “Discovering how well it can be described by the second contained superconducting state made us understand that common imperfect fits were not just due to noisy data or temperature, but due to underlying fundamental physics.”
Superconductors are materials that can carry electrical current without energy loss under certain conditions. A central challenge for researchers is understanding how electrons pair inside these materials and how those pairs create superconductivity.
NbSe2 is one of the most studied two-dimensional superconductors — materials that can be reduced to only a few atomic layers while maintaining superconducting properties. For years, experiments suggested that ultrathin NbSe2 had a single superconducting energy gap, a measurement that shows how much energy is required to break apart the paired electrons responsible for superconductivity.
The new study showed that this single-gap model was incomplete. The material contains a second interacting superconducting state that had previously gone undetected. The two states interact so strongly that conventional measurements interpreted them as a single superconducting state.
The same hidden behavior was also found in another related material, tantalum disulfide (TaS2), suggesting that the phenomenon may extend beyond a single material.
Uncovering the Hidden State
Using a highly sensitive technique called tunneling spectroscopy, which measures the energy behavior of electrons at extremely low temperatures, the team detected subtle features in the superconducting energy spectrum that earlier experiments had missed. The researchers compared the discovery to hearing what sounds like a single singer, only to discover it is actually a perfectly synchronized duet.
Simon explained to TPS-IL that previous experiments likely missed the second superconducting state because the effect was subtle and required more precise measurements.
“Previous experiments did not detect the second superconducting order due to a few factors,” Simon said. “First, they mostly measure at temperatures higher than 25 mK. In addition, only taking into account one superconducting state gives a pretty good approximation for most purposes and for most measurement resolutions.”
The researchers overcame these limitations by fabricating high-quality devices and measuring them at temperatures of about 25 millikelvin, allowing them to observe finer details in the superconducting spectrum.
The discovery may influence how scientists interpret unexplained results in superconductivity research. Simon told TPS-IL that data that does not fit established models may indicate undiscovered physical processes rather than experimental problems.
“This understanding could possibly influence how scientists view ill-fitting data that does not fit the expected model,” Simon stressed. “Such data can actually be a sign of a more complex superconductivity landscape.”
While the discovery does not immediately translate into a new technology, it could improve scientists’ understanding of superconducting materials used in future quantum technologies, superconducting circuits and advanced electronics.
The team’s next steps will focus on using this improved understanding of NbSe2 to explore additional unusual behaviors, including responses under different magnetic conditions and interactions with other materials.
The findings were published in the peer-reviewed Physical Review Letters.
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