Researchers revealed a bizarre quantum link between carbyne and carbon nanotubes—two materials that shouldn’t “talk” but somehow do. The discovery could reshape how we design ultra-sensitive nano-devices.
To design the next generation of smart materials, scientists need to understand how atoms interact at the tiniest scales. That means diving into the strange world of quantum mechanics, where particles behave in ways that often defy intuition. One puzzle that has baffled researchers for years involves carbyne, a chain of carbon atoms, and its curious behavior when placed inside a carbon nanotube.
Now, a team of scientists from Austria, Italy, France, China, and Japan, led by the University of Vienna, has cracked the mystery. Using powerful tools like Raman spectroscopy, advanced theoretical models, and breakthroughs in machine learning, they’ve revealed surprising new insights into how carbyne behaves. Their findings, published in Nature Communications, suggest that carbyne could become a powerful tool for sensing minute changes in its environment, opening the door to a new class of ultra-sensitive nanoscale sensors.
Seeing Vibrations With Light
To uncover these effects, the researchers used Raman spectroscopy—a technique that lets scientists “see” how atoms vibrate by observing how light scatters off a material. These vibrations, or vibrational eigenstates, are deeply connected to a material’s properties, from how it conducts electricity to how it stretches or reacts to heat. Understanding these hidden vibrations is key to developing materials with highly specific functions.
The Surprise Discovery of Carbyne
Back in 2015, researchers at the University of Vienna made a groundbreaking discovery. They managed to stabilize carbyne for the first time by placing it inside protective carbon nanotubes. This slender carbon chain has incredible potential. It could be the strongest material ever created, and it has unique electronic features that could revolutionize semiconductor technology.
But something unexpected happened during those early experiments. The scientists observed a strange system state—one that didn’t fit any known models. It left the community puzzled, unsure of what exactly they were seeing.
Machine Learning Unlocks a Paradox
The researchers have now taken a closer look at this inexplicable system state. Using an innovative theoretical model, which could only be applied thanks to recent breakthroughs in machine learning, they were able to find an explanation for the novel interactions between the chain and nanotube observed in the laboratories, which initially seems paradoxical.
“Although the chain and the nanotube are electronically isolated and therefore do not exchange electrons, they are subject to an unexpectedly strong coupling between the vibrations of the two nanostructures,” explains Emil Parth from the University of Vienna, lead author of the study published in Nature Communications.
In other words, the carbyne and nanotube talk to each other electronically, while at the same time they are electronically isolated in the classical sense. This quantum mechanical coupling of vibrations is usually negligible, but in this particular case, it is outstandingly strong due to the intrinsic electronic properties and structural instability of the chain.
Carbyne’s Powerful Sensing Potential
This is what makes the chain so interesting, as it reacts strongly to external influences. It therefore interacts strongly with the nanotube surrounding it. The new study shows that this interaction is surprisingly not one-sided, as the carbyne also changes the properties of the nanotube, albeit in a different way than previously assumed. “The sensitivity of carbyne to external influences is crucial for its potential application in future materials and devices as a contactless optical sensor on the nanoscale, for example, as a local temperature sensor for heat transport measurements,” concludes Thomas Pichler, head of the research group at the University of Vienna.
Reference: “Anharmonic effects control interaction of carbyne confined in carbon nanotubes shaping their vibrational properties” by Emil Parth, Andrea Corradini, Weili Cui, Davide Romanin, Christin Schuster, Clara Freytag, Lei Shi, Kazuhiro Yanagi, Matteo Calandra and Thomas Pichler, 26 May 2025, Nature Communications.
DOI: 10.1038/s41467-025-59863-3
The work was supported by the EU via an ERC-SYN grant MORE-TEM.
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