Imagine a liquid that moves endlessly, without resistance — so smooth that it seems to defy the laws of physics. Researchers at UBC have observed this rare phenomenon in a molecular system for the first time.
Superfluidity is a unique state of matter in which a liquid flows without friction. An object placed in this liquid can move freely within it, not experiencing resistance. This intriguing behaviour occurs at temperatures close to 0 K, but had previously only been observed in helium.
However, UBC researchers have presented strong new evidence that hydrogen can also become superfluid, which opens doors to new understandings of quantum matter. The idea of hydrogen superfluidity goes back to the 1970s, but has remained theoretical until now.
“We started this research [around] 20 years ago,” said Dr. Takamasa Momose, a UBC chemistry professor and the study’s lead investigator, in an interview with The Ubyssey. “It took quite some time to analyze the data because it's a very small effect, and we have to extract that superfluid nature in the observed spectrum … Many students contributed to this work.”
Hydrogen is especially intriguing in this context — superfluidity occurring in a molecule as basic as H₂ marks the first time such behaviour has been observed outside atomic systems like helium.
The team experimented by placing one methane molecule into a cluster of hydrogen molecules cooled to near absolute zero in helium nanodroplets. Then, using laser radiation to spin the methane molecules, they observed the rotations. This approach mimicked placing a spinning object in a liquid to see if it encounters resistance — a noninvasive way to detect superfluid behaviour without disturbing the delicate system, which was a limitation in earlier studies.
According to Momose, methane was ideal to use in this study because it is spherical and has no dipole moment. A dipole moment happens when there is an unequal distribution of electrons across a molecule, resulting in a polar molecule. “And because it’s spherical, it does not add up too much to the observed superfluid nature of hydrogen,” said Momose.
If the surrounding hydrogen were acting like a normal fluid, it would slow the methane down. But in a superfluid, the methane would spin freely — and that’s exactly what researchers observed.
Measuring such small changes in rotation was challenging. The team had to precisely control the number of hydrogen molecules in each cluster and repeat their experiments several times under highly sensitive conditions. Even small shifts in cluster size could influence the results.
“[The nozzle] is very sensitive to any kind of force,” said Chie Nakayama, a graduate student in the lab. “We’re using it in a vacuum chamber, so we can’t just change it on the go. We have to set it to some condition, close the chamber, vacuum pump it and then see how it performs at low temperatures. The [optimization] process is quite long.”
The team used high-resolution laser spectroscopy, a technique that analyzes molecules and atoms using focused laser light that excites samples and measures the emitted light to provide information on energy levels and transitions. It is used to gather rotational data, producing spectra with clear, reproducible patterns.
These patterns showed that hydrogen has the potential to behave frictionlessly even beyond a cluster size; in the superfluid state, many hydrogen molecules move together like a single wave, governed by the same quantum function.
Understanding this quantum behaviour helps scientists explore how matter behaves in extreme conditions while showing that the observation of molecular superfluidity was previously thought to be out of reach.
Looking ahead, this research could have real-world applications. Hydrogen has already been explored globally as a clean-burning energy source. Canada has access to low-cost hydrogen resources and abundant clean electricity for hydrogen production from nuclear, wind and solar sources.
These molecules are interesting to researchers and are a clean energy source that is valuable for the environment. According to Momose, if superfluid hydrogen could one day be used on a larger scale, it might open up new, energy-efficient methods for transport by optimizing hydrogen storage.
While the work is still in early experimental stages, it could represent a foundational step toward a more sustainable future. The team’s research reveals a fascinating world of superfluidity, inviting UBC students to explore its potential applications.
"[Nakayama] is now working on different projects, studying [the] interaction between chiral molecules using the same technique … There are many applications of this research technique in the field of physical chemistry and physics,” said Momose.
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