Researchers at the Hebrew University of Jerusalem have discovered that niobium diselenide (NbSe2) conceals two distinct superconducting orders that interact so strongly they appear as a single state. Published in Physical Review Letters, the finding resolves a long-standing physics puzzle regarding the material’s energy spectrum under tunneling spectroscopy measurements.
Deconstructing the Single-Singer Illusion in Niobium Diselenide
Physics often relies on models that assume simplicity until experimental friction proves otherwise. For decades, researchers investigating superconductors—materials capable of carrying electrical current with zero energy loss—relied on standard frameworks to map how electrons pair up to eliminate resistance. One of the best-studied examples in this domain is niobium diselenide, or NbSe2.
When scientists reduced NbSe2 down to just a few atomic layers, initial experiments pointed to straightforward behavior. The material appeared to possess a single energy gap, the classic signature of a unified superconducting order. Yet, experimental anomalies persisted. Traditional theoretical models continually failed to replicate the exact shape of the superconducting energy spectrum recorded in laboratories.
The solution required a closer look at the microscopic architecture. Led by PhD student Shahar Simon and MSc student Maya Klang under the guidance of Prof. Oded Millo and Prof. Hadar Steinberg from the Racah Institute of Physics and the Center for Nanoscience and Nanotechnology at the Hebrew University of Jerusalem, a research team deployed highly sensitive tunneling spectroscopy measurements to peer deeper into the system.
The instruments revealed an unexpected reality. Instead of a single superconducting order, the few-layer NbSe2 harbors two distinct states operating in tandem.
“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 explained when describing the phenomenon.
Applying Advanced Models to Conflicting Spectroscopy Data
Uncovering the hidden duet required upgrading the mathematical frameworks used to interpret tunneling spectroscopy. By deploying a more advanced model that integrates two distinct superconducting orders, the Hebrew University team successfully accounted for the anomalous energy spectra. Furthermore, this dual-order model accurately predicted how the materials respond when external magnetic fields are applied.
The implications extend beyond NbSe2 alone. Using the same experimental and analytical approach, the researchers identified identical concealed behavior in a closely related material, tantalum disulfide (TaS2). The duplication of results across material boundaries suggests that hidden multi-order superconductivity may be a broader characteristic of layered quantum materials than previously understood.
The complexity scales upward when examining thicker variants of these materials. According to the study’s findings, bulk NbSe2 may actually house three interacting superconducting orders. This layering of microscopic states demonstrates that superconductivity in these materials is richer than previously recognized.
Architecting the Future of Quantum Computing and Ultra-Efficient Electronics
Unmasking this hidden structural complexity is not merely an academic exercise. As scientists pursue scalable quantum computers, ultra-efficient electronics, and advanced sensors, precision control over electron pairing is paramount.
Gaining a granular understanding of how multiple superconducting orders interact within atomic layers gives material scientists a new blueprint. Rather than treating these materials as monolithic blocks, future device engineers could theoretically design superconducting materials and devices with tailored order interactions, optimizing them for specific computational thresholds or magnetic sensitivities.
As research shifts from macroscopic observation to atomic-level manipulation, studies like the one conducted at the Hebrew University provide the foundational physics required to engineer the next generation of high-performance microelectronics.
