Physicists Observe Exotic Quantum Supersolid State at Room Temperature

An international team of physicists has successfully observed an exotic quantum state of matter known as a supersolid within an exciton-polariton Bose-Einstein condensate at room temperature. The breakthrough, recently published in the journal Science Advances, represents a significant departure from previous experiments that required extreme cooling conditions approaching absolute zero.

The newly observed state is characterized as part liquid and part solid. In the quantum realm, a superfluid is defined as a liquid capable of flowing without resistance, while a supersolid combines superfluidity with a regular, repeating crystal structure. Furthermore, an exciton-polariton acts as a hybrid quasiparticle joining light and matter, and a Bose-Einstein condensate occurs when multiple particles merge into a single quantum entity.

To produce this paradoxical phase of matter, the researchers utilized a tiny light-trapping structure called a microcavity. The experimental setup combined a voltage-controlled liquid crystal with an organic semiconductor that interacts strongly with light. Laser pulses were then applied to supply the necessary energy for the quantum reaction to take place.

According to the research team, the liquid-crystal microcavities are capable of operating at temperatures approaching 60 degrees Celsius, or 140 degrees Fahrenheit. This setup provides an inexpensive and controllable environment that eliminates the need for a cryogenic refrigerator, offering a practical alternative for studying complex quantum behavior.

During the experiments, the researchers observed that successive laser pulses caused the condensate to reform with its crystalline stripes lining up in slightly different places each time. This behavior provided clear evidence of spontaneous symmetry breaking. Physicist Guillaume Malpuech of the French National Centre for Scientific Research described it as a textbook example, noting that theory predicted the supersolid could choose among several equivalent states.

Despite the successful observations, the physical behavior was notably short-lived. The semiconductor reacted with the liquid crystal over time, causing the materials to degrade and limiting individual particle lifespans to mere fractions of a second. Because repeating a measurement required fabricating an entirely new sample, the team had to plan their sequence of experiments meticulously in advance.

Researchers believe this simplified method for studying superfluids and supersolids could pave the way for advancements in quantum technology. Potential long-term applications include the development of advanced computer chips, high-performance optical sensors, and new insights into spin-orbit coupling and quantum fluids of light.