Physicists Make Exotic Supersolid at Room Temperature, No Deep Freeze Needed

An international team of physicists says it has created an exotic quantum state of matter called a supersolid without the extreme cooling that such states usually demand. According to ScienceAlert, the results were published in the journal Science Advances and could eventually make quantum technology more practical.

The state appeared inside a tiny light-trapping structure called a microcavity. The researchers say this setup is relatively inexpensive, can be controlled with voltages and does not need a cryogenic fridge.

What exactly did the researchers create?

The technical name is a supersolid in an exciton-polariton Bose-Einstein condensate. Each part of that name has a plain meaning, as ScienceAlert explains it.

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. Put together, the result is a state that is part liquid and part solid.

How was it made?

The team 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.

Physicist Wiktor Piecek of the Military University of Technology in Poland said the liquid-crystal microcavities can operate at temperatures approaching 60 °C (140 °F). That is well above the ultracold conditions normally needed for quantum states.

How do they know it is a supersolid?

The key evidence came from repeated laser pulses. Each time, the condensate reformed, and its stripes, the crystal-like part of the supersolid, lined up in slightly different places. According to the report, this suggests the pattern comes from the quantum state itself and not from the microcavity shaping it.

Physicist Guillaume Malpuech of the French National Centre for Scientific Research (CNRS) called it “a textbook example of spontaneous symmetry breaking.” He said theory predicted the supersolid could choose among several equivalent states, and that is what the team observed.

The team tested multiple samples with the same results, and computer simulations backed up the findings. The researchers also saw quantum vortices, which are flaws in the stripe pattern that indicate superfluid behavior.

What are the limits of the result?

The behavior was short-lived. The materials degraded over time because the semiconductor reacted with the liquid crystal, and the particles themselves lasted only fractions of a second. That was enough for the measurements, according to ScienceAlert.

The setup also made experiments awkward. Physicist Marcin Muszyński of the City College of New York said the team had to plan the entire sequence in advance, because repeating a measurement meant fabricating a new sample.

Why does it matter?

This is basic laboratory research, not a product, and no practical device has been announced. The significance lies in the method. The researchers say it offers an easier way to study quantum behavior in superfluids and supersolids without the cost and complexity of extreme cooling. That applies particularly to spin-orbit coupling, the link between light polarization and motion that produced the supersolid arrangement.

ScienceAlert reports that almost any quantum effect involving light could benefit further down the line, including effects related to computer chips and advanced sensors. The authors write in their paper that the work opens new perspectives for quantum fluids of light in the presence of spin-orbit coupling and beyond.

What comes next?

The report names two possible directions. One is finding ways to make the core reactions last longer. The other is examining the quantum vortices in more detail.

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Around Prague, based on reporting by ScienceAlert