A Supersolid at Room Temperature, Made From Light and Matter
It sounds impossible: a substance that flows without any friction, like a perfect liquid, while also arranging itself into a regular pattern, like a crystal. Yet quantum physics predicted exactly that combination in the 1960s — a state of matter called a supersolid. For more than fifty years it stayed a prediction, then it was seen only in atoms chilled to near absolute zero. Now researchers have observed a supersolid at room temperature, using particles that are part light and part matter.
The team, from the Faculty of Physics at the University of Warsaw, the Military University of Technology in Poland, IBM Research Zurich and the French National Centre for Scientific Research (CNRS), reports the result in Science Advances.
A liquid that is also a crystal
The story starts with superfluidity: a state in which viscosity — the internal friction of a fluid — disappears completely. A superfluid can flow through the narrowest channels without resistance. Physicists predicted that a superfluid could at the same time develop a periodic, crystal-like structure. The result, a supersolid, keeps the frictionless flow of a superfluid while showing the spatial order of a crystal.
It was not until 2017 that supersolidity was first observed experimentally, in ultracold atomic Bose-Einstein condensates — clouds of atoms cooled until they behave as a single quantum object. Those experiments needed expensive cryogenic systems working close to absolute zero, the coldest possible temperature.
The new work takes a completely different route. Instead of ultracold atoms, the researchers studied exciton polaritons: hybrid quasiparticles formed when light couples strongly with matter inside an optical microcavity — two mirrors facing each other, a tiny distance apart. Polaritons live for only a few picoseconds, trillionths of a second, but that is long enough for them to form a Bose-Einstein condensate and behave as a quantum superfluid.
The microcavity was filled with a specially designed liquid crystal and coated with an organic semiconductor, a combination that allows strong light-matter coupling at room temperature. "Our liquid-crystal microcavities can operate even at temperatures approaching 60°C," said Professor Wiktor Piecek of the Military University of Technology, whose group developed the liquid-crystal structures.
How do you recognise a supersolid?
The clue was in the light coming out of the sample. As the condensate entered the supersolid phase, regularly spaced bright fringes appeared — evidence that it had spontaneously formed a periodic pattern in its density, the hallmark of crystallisation.
Then came something even more striking. With every laser pulse that excited the sample, the fringes appeared in a different position. Each time, the quantum system independently chose one of many equivalent arrangements. "This is a textbook example of spontaneous symmetry breaking," explained Professor Guillaume Malpuech of Institut Pascal (CNRS). "Theory predicted that the supersolid could choose among several equivalent states, and that is exactly what we observed."
At the same time, the condensate showed a persistent spin helix — a periodic pattern in the polarisation of the emitted light. The researchers therefore saw two kinds of order at once: one in the light's intensity, one in its polarisation.
The experiment was a race against time. The organic semiconductor gradually reacted with the liquid crystal, so all measurements had to be finished within a few hours of assembling each sample. "We had to plan the entire sequence of experiments in advance," recalled Dr Marcin Muszyński, the paper's first author, now a postdoctoral researcher at The City College of New York. "Repeating a measurement meant fabricating an entirely new sample."
Why room temperature matters
Until now, studying exotic quantum phases has mostly meant working near absolute zero. Showing that similar phenomena can be explored in photonic systems at room temperature opens the door to future quantum technologies based on light — from ultrafast photonic devices and computing inspired by the brain to highly sensitive optical sensors.
Just as importantly, liquid-crystal microcavities are the first electrically tunable platform for studying supersolid polariton condensates: their optical properties can be adjusted with an external voltage, giving researchers a flexible way to explore quantum phases of light and matter and a path towards practical quantum photonic devices.
This is not a gadget you can buy, and the researchers make no such claim. It is a new laboratory window onto a state of matter that textbooks said should exist — now visible, at room temperature, in light itself.
If your child is learning about states of matter and wonders whether solid, liquid and gas are really the whole story, a first lesson in physics can start with a supersolid: a substance that refuses to choose. Book your first lesson
Sources:
- Muszyński, M. et al., "Observation of a supersolid phase in a spin-orbit coupled exciton-polariton Bose-Einstein condensate", Science Advances (2026), DOI: 10.1126/sciadv.aee4875, as reported 3 November 2026: https://phys.org/news/2026-11-hybrids-supersolid-quantum-state-room.html
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