Supersolid at room temperature: Polish team sees new quantum phase
Polish physicists have seen a supersolid, a state that acts like a crystal and a frictionless fluid at once, at room temperature. Until now it needed extreme cold.
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giftdetect· the right gift in minutesA supersolid sounds like a contradiction, and for decades it was a hard one to catch. Now a team that includes researchers from the University of Warsaw and the Military University of Technology (WAT) has observed one at room temperature, no deep-freeze equipment required. The results appeared in Science Advances.
A supersolid is a quantum phase of matter that combines two things that seem to exclude each other. It has the orderly, repeating structure of a crystal, and it also has superfluidity, meaning it flows without any viscosity. In effect, the material behaves like a crystal and a perfect quantum liquid at the same time. The idea dates back to the 1960s, but the first observation came only in 2017, in ultracold atomic gases.
How did they make a supersolid at room temperature?
The team used light instead of cold atoms. They built an optical microcavity, a tiny structure that traps light, filled with a nematic liquid crystal and placed between layers of an organic semiconductor and Bragg mirrors. This let light and matter couple strongly, producing quasiparticles called exciton polaritons. Under the right conditions these form a Bose-Einstein condensate, a collective quantum state that shows superfluid behaviour.
The researchers also developed a way to control the system electrically. Changing the voltage alters the birefringence of the liquid crystal, which lets them tune the system and the polarisation of the condensate.
What did the experiment show?
The evidence was regular bright stripes in the light emitted by the sample. They point to spontaneous, periodic changes in the condensate's density, much like atoms lining up in a crystal. The polarisation of the light was modulated too, so two kinds of order appeared together.
After successive laser pulses, the stripe pattern showed up in different positions. The system picked one of several equivalent configurations on its own, a sign of spontaneous symmetry breaking.
Why it matters: studying exotic phases without cooling to near absolute zero is far cheaper. The authors point to possible uses in photonic devices, neuromorphic computing accelerators (hardware inspired by how brains process information) and very sensitive optical sensors.
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