Schematic representation of carbyne stabilized inside double-walled carbon nanotubes with a small diameter. Emil Parth, Faculty of Physics, University of Vienna
Researchers have resolved a puzzling vibrational phenomenon that has baffled the scientific community for years, after discovering a strange quantum link between carbyne and carbon nanotubes.
Led by the University of Vienna in Austria, along with researchers from Italy, France, China, and Japan, the study sheds new light on how carbynes, crystalline forms of carbon linked in chains with alternating single and triple bonds, interact with nanotubes on a quantum level.
For the research, the scientists relied on Raman spectroscopy, a non-destructive chemical analysis technique which is commonly used in research to identify molecules by their unique structural fingerprint.
After additionally applying innovative theoretical models, as well as machine learning, they were able to demonstrate the universal applicability of carbyne as a sensor due to its sensitivity to external influences.
Nearly a decade in the making
Understanding how matter behaves at the atomic scale is crucial for developing the materials of the future. According to the scientists, quantum mechanical effects, such as electron movement, atomic vibrations, and energy band structures, shape how materials conduct electricity, respond to magnetic fields, transmit light, or withstand mechanical stress.
To better understand these mechanisms, the scientists revisited a surprising discovery made nine years ago by Thomas Pichler, PhD, a physics professor at the University of Vienna, and head of the research group.
At the time, Pichler and his team managed to stabilize carbyne, an ultra-thin chain of carbon atoms, inside carbon nanotubes, for the first time, marking a breakthrough that stunned the scientific community.
Carbyne, which had previously only been detected in a single tube, exhibits controllable electronic properties vital for semiconductor technology and may be the strongest known material in terms of tensile strength. But, during the experiment, the team observed a puzzling vibrational system state that couldn’t be explained by existing models and was completely misunderstood at the time.
That has now changed, after researchers, led by Emil Parth, MSc, a University of Vienna physicist, and lead author of the study, took a closer look at the previously unexplained state, and finally found answers. They now used an innovative theoretical model enabled by recent breakthroughs in machine learning.
Next-gen optical devices
Despite the result appearing contradictory at first, the team was ultimately able to explain the newly found interactions between the carbon chain and the nanotube.
“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,” Parth, said.
The physicist explained that carbyne and the nanotube interact electronically while remaining electronically isolated at the same time. While it may seem like this kind of quantum mechanical coupling is usually negligible, it is remarkably strong in this situation, due to the chain’s intrinsic electronic properties and structural instability.
The team believes this makes the chain particularly intriguing, as it not only reacts strongly to external stimuli but also interacts with the surrounding nanotube. Moreover, the study suggests that the interaction is not one-sided, as carbyne also alters the properties of the nanotube, though in a way that differs from previous assumptions.
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“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,” Pichler concludes in a press release.
The study has been published in the journal Nature Communications.
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