Scientists Discover Two Superconducting States Hiding as One in Ultrathin Materials

Physicists at the Hebrew University of Jerusalem found that niobium diselenide and tantalum disulfide — long thought to have a single, simple superconducting state — actually contain two strongly interacting states masquerading as one. The discovery, published in Physical Review Letters, resolves a years-old puzzle about their energy spectra.

Key Takeaways

Physicists at the Hebrew University of Jerusalem found that niobium diselenide and tantalum disulfide — long thought to have a single, simple superconducting state — actually contain two strongly interacting states masquerading as one.
The discovery, published in Physical Review Letters, resolves a years-old puzzle about their energy spectra.

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A team of physicists at the Hebrew University of Jerusalem has uncovered hidden complexity inside two ultrathin superconductors that researchers had long considered well understood. Niobium diselenide (NbSe2) and tantalum disulfide (TaS2) were found to each contain two distinct superconducting states that interact so strongly they appear as a single state in most measurements.

Using highly sensitive tunneling spectroscopy, PhD student Shahar Simon and MSc student Maya Klang, guided by Professors Oded Millo and Hadar Steinberg, found that what appeared to be a single energy gap — a key characteristic reflecting how electrons pair together to move without resistance — was actually the product of two different superconducting orders working in perfect synchrony.

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

The finding, published in Physical Review Letters, resolves a long-standing puzzle: traditional theories could not fully reproduce the detailed shape of the superconducting energy spectrum seen in earlier experiments. The new two-order model explained the measurements much more accurately, including the materials' behavior under magnetic fields.

The results point to even greater complexity in thicker forms of the material. According to the findings, bulk NbSe2 may contain three interacting superconducting orders, suggesting that superconductivity in these materials is richer than previously recognized.

Uncovering this hidden structure could eventually allow researchers to design superconducting materials and devices with greater precision, as scientists pursue quantum computers, ultra-efficient electronics, and advanced sensors.