New study reveals that two widely studied ultrathin superconducting materials are more sophisticated than they appear. Although they seem to behave like simple superconductors with a single energy gap, they actually contain two strongly interacting superconducting states that work together and disguise themselves as one. This finding resolves a long-standing mystery about how these materials behave, providing new insight into superconductivity that could help scientists design better superconducting materials for future technologies such as quantum computers, ultra-efficient electronics, and advanced sensors.

Sometimes, the biggest scientific discoveries come from looking more closely at something we thought we already understood.

For decades, physicists have studied a remarkable class of materials called superconductors—materials that can carry electricity with zero energy loss. These materials could one day help power ultra-efficient electronics, quantum computers, and advanced medical technologies.

One of the most widely studied superconductors, niobium diselenide (NbSe₂), seemed straightforward when peeled down to just a few atomic layers. Experiments suggested it behaved like a superconductor with a single energy gap—a fundamental fingerprint that describes how electrons order in pairs, to flow without resistance.

But researchers suspected there was more to the story. The study, led by PhD. student Shahar Simon and MSc. student Maya Klang under the guidance of Prof. Oded Millo, and Prof. Hadar Steinberg of the Racah Institute of Physics and the Center for Nanoscience and Nanotechnology at the Hebrew University of Jerusalem, was published in Physical Review Letters.

Using extremely sensitive tunneling spectroscopy measurements, the team found that the material wasn't behaving like a simple, single-order superconductor at all. Instead, it was hiding two different superconducting orders that interact so strongly they appear as one. The same hidden behavior was also found in another closely related material, TaS₂.

"It's a bit like listening to what sounds like a single singer, only to discover it's actually a perfectly synchronized duet," said the researchers.

The discovery solves a long-standing puzzle. Previous experiments could not fully explain the detailed shape of the superconducting energy spectrum using traditional theories. By applying a more sophisticated model, accounting for the presence of two different superconduting orders, the Hebrew University team was able to accurately explain not only the measurements themselves, but also how the materials respond when exposed to magnetic fields.

The findings also suggest that the thicker, bulk version of NbSe₂ may actually contain three interacting superconducting orders, revealing an even richer picture of how superconductivity works in these materials.

Understanding this hidden complexity could help scientists design and engineer future superconducting devices with greater precision. As researchers work toward technologies such as quantum computers and ultra-efficient electronic devices, knowing exactly how electrons behave inside these materials becomes increasingly important.