Physicists Create Room-Temperature Supersolid Quantum State

What researchers created

An international team of physicists has created an exotic quantum state of matter called a supersolid in an exciton-polariton Bose-Einstein condensate, operating at room temperature without the extreme cooling that such states usually require. The results were published in the journal Science Advances.

The state is part liquid and part solid. A superfluid is a liquid that flows without resistance. A supersolid is a superfluid that also has a regular, repeating crystal structure instead of a loose, fluid one. An exciton-polariton is a hybrid quasiparticle, meaning several particles acting as one, that combines light and matter. In a Bose-Einstein condensate, many particles or quasiparticles merge into a single quantum entity.

How it was made

The researchers combined a liquid crystal, which can be controlled with voltage, and an organic semiconductor, which interacts strongly with light. Laser pulses supplied the energy to trigger the quantum behavior. The state appeared inside a tiny light-trapping structure called a microcavity.

The setup is relatively inexpensive, can be controlled with voltages, and does not need a cryogenic fridge. Physicist Wiktor Piecek from the Military University of Technology in Poland said: "Our liquid-crystal microcavities can operate even at temperatures approaching 60 °C (140 °F)."

Evidence and limitations

The behavior was relatively short-lived. The materials degraded over time because the semiconductor reacted with the liquid crystal. The individual particles produced by the researchers lasted for fractions of a second.

Physicist Marcin Muszyński from the City College of New York said: "We had to plan the entire sequence of experiments in advance." He added that repeating a measurement meant fabricating an entirely new sample.

Further validation came with each successive laser pulse. The condensate reformed each time, with its stripes—the solid, crystal-like part of the supersolid—lining up in slightly different places with every refresh. Physicist Guillaume Malpuech from the French National Centre for Scientific Research (CNRS) said: "This is a textbook example of spontaneous symmetry breaking." He added: "Theory predicted that the supersolid could choose among several equivalent states, and that is exactly what we observed."

Multiple samples were tested with the same results, which were also backed up by computer simulation models. The researchers also observed quantum vortices—flaws in the stripe patterns that indicated superfluid behavior.

Why it matters

The researchers say the work opens new perspectives for quantum fluids of light physics in the presence of spin-orbit coupling and beyond. Spin-orbit coupling is the linking of light polarization and motion that created the supersolid arrangement.

The method offers an easier way to study quantum behavior in superfluids and supersolids without the added expense and complexity of extreme cooling. Almost any quantum effect involving light, including those related to computer chips and advanced sensors, could benefit further down the line.

Routes for developing the experiments further might involve working on ways to get the core reactions to last for longer, and interrogating in more detail the quantum vortices that appeared.

Sources

• sciencealert.com: Finally! Physicists Create an Exotic Quantum State of Matter That Works at Room Temperature : ScienceAlert
• aroundprague.cz: Physicists Make Exotic Supersolid at Room Temperature, No Deep Freeze Needed

This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.