Physicists push quantum boundaries by turning a superfluid into a supersolid — and back — for the first time
Scientists have just observed a bizarre phase of matter transform into an even stranger phase. For the first time, they saw a superfluid transform into a supersolid – a transition they weren’t even sure was possible.
In a January 28 study in the journal NatureThe researchers observed a group of excitons – quasiparticles that combine an electron and an electron hole – transforming from a superfluid to a supersolid and back again. This is the first time that excitons have condensed into a supersolid, undergoing a reversible phase transition, just as water can transform from a liquid to ice and vice versa.
Secret phases of matter
There are many others phases of matter than the three typical states we encounter daily (gases, liquids, and solids), although most of these other states of matter only exist in extreme conditions. Superfluids are a type that only occur when certain particles, like helium isotopes and excitons, are cooled just above. absolute zero — the total absence of heat. They’re not quite liquids – they flow without frictional resistance – and when agitated they form tiny Eternal tornadoes called quantum vortices.
Supersolids, on the other hand, are a state of matter that would exist when superfluids are cooled even further. They retain the zero viscosity of superfluidity, but instead of particles moving in a liquid-like drop, they form an ordered structure, like a crystal lattice, while retaining their ability to flow and form quantum vortices.
Supersolids have been made in the lab before, including in 2021, when researchers created 2D supersolid dysprosium and in 2024, when they observed quantum vortices in a supersolid. However, they only achieved this by using additional equipment and energy to force the particles into an ordered array. The new study, in contrast, demonstrates a natural phase transition.
“For the first time, we have seen a superfluid undergo a phase transition to become what appears to be a supersolid.” Cory Deanphysicist at Columbia University and co-author of the study, said in a statement.
Explore new frontiers
To do this, the researchers brought together two pieces of graphene, which resemble a very thin sheet of paper composed entirely of carbon atoms. Then, they added a strong magnetic field and cooled the system to form a “soup” of excitons.
When cooled to 2.7 to 7.2 degrees Fahrenheit (1.5 to 4 degrees Celsius) above absolute zero, the excitons form a superfluid. When cooled more than that, the excitons transform into a mysterious, electrically insulating new phase that the team suspects is the theorized supersolid state.
“Superfluidity is generally considered to be the ground state at low temperatures.” Jia Liphysicist at the University of Texas at Austin and co-author of the study, said in the release. “The observation of an insulating phase melting in a superfluid is unprecedented. This strongly suggests that the low-temperature phase is a very unusual exciton solid.”
The team is investigating other materials to test and finding new ways to measure and study the exciton supersolid state.
“For now, we are exploring the limits around this insulating state, while building new tools to measure it directly,” Dean said. Further studies will help scientists understand the behavior of supersolids and superfluids, deepen our understanding of particle physics, and work on higher temperature supersolid applications.
Zeng, Y., Sun, D., Zhang, NJ, Nguyen, RQ, Shi, Q., Okounkova, A., Watanabe, K., Taniguchi, T., Hone, J., Dean, CR, & Li, JIA (2026). Observation of a superfluid-insulator transition of bilayer excitons. Nature. https://doi.org/10.1038/s41586-025-09986-w
