Scientists simply observed a strange phase of matter transform into an even stranger phase. For the first time, they witnessed a superfluid transform into a supersolid. I wasn’t even sure this transition was possible.
In a study published January 28 in the journal Nature, researchers observed groups of excitons (quasiparticles that combine electrons and electron holes) changing from a superfluid to a supersolid and back again. This is the first time excitons have been observed to condense into a supersolid and undergo a reversible phase transition, similar to how water changes from liquid to ice and back again.
secret stages of matter
There are many more phases of matter than the typical three we encounter every day (gas, liquid, and solid), but most of these other states of matter exist only under extreme conditions. A superfluid is a type of fluid that only occurs when some particles, such as helium isotopes or excitons, are cooled to a temperature just above absolute zero, or in the complete absence of heat. They are not perfect liquids and flow without frictional resistance. And when stirred, they form tiny eternal tornadoes called quantum vortices.
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A supersolid, on the other hand, is a state of matter that is theorized to exist when a superfluid is further cooled. They retain the zero viscosity of superfluidity, but form regular structures like crystal lattices, while maintaining the ability for particles to flow and form quantum vortices, rather than moving around in a liquid-like mass.
Supersolids have been created in the lab before: in 2021, researchers created the 2D supersolid dysprosium, and in 2024, quantum vortices were observed inside the supersolid. However, they achieved this only by using additional equipment and energy to force the particles into a regular lattice. In contrast, new research shows a natural phase transition.
“This is the first time we have seen a superfluid undergo a phase transition to become what appears to be a supersolid,” Corey Dean, a physicist at Columbia University and co-author of the study, said in a statement.
Exploring new boundaries
To do this, the researchers placed two sheets of graphene (a very thin piece of paper made entirely of carbon atoms) very close together. They then applied a strong magnetic field to cool the system, forming a “soup” of excitons.
When cooled to 2.7 to 7.2 degrees Fahrenheit (1.5 to 4 degrees Celsius) below absolute zero, the excitons formed a superfluid. When cooled further, the excitons transform into a mysterious new electrically insulating phase that the researchers suspect is the theoretical supersolid state.
“Superfluidity is generally considered a low-temperature ground state,” Jia Li, a physicist at the University of Texas at Austin and co-author of the study, said in a statement. “The observation of an insulating phase soluble in a superfluid is unprecedented. This strongly suggests that the low-temperature phase is a very unusual exciton solid.”
In addition to finding new ways to measure and study the supersolid state of excitons, the research team is also looking to test other materials.
“For now, we are investigating the boundaries around this insulating state while building new tools to directly measure it,” Dean said. Further research will help scientists understand how supersolids and superfluids behave, deepen our understanding of particle physics, and work toward higher-temperature supersolid applications.
Zeng, Y., Sun, D., Zhang, N.J., Nguyen, R.Q., Shi, Q., Okounkova, A., Watanabe, K., Taniguchi, T., Hone, J., Dean, CR., and Li, JIA (2026). Observation of the superfluid-to-insulator transition of double-layer excitons. Nature. https://doi.org/10.1038/s41586-025-09986-w
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