European Researchers Observe a Room-Temperature Supersolid State in Light-Matter Hybrids
Physicists in Poland, France, and Switzerland demonstrate an electrically tunable supersolid using liquid-crystal microcavities without near-absolute-zero cooling
A European research team has observed an electrically tunable supersolid state of matter at room temperature inside an optical cavity. The physics discovery, achieved by combining liquid crystals and organic semiconductor films, demonstrates that supersolid behavior can occur without the ultracold refrigeration previously required for such quantum phases.
Light and matter create a dual-order quantum phase
Physicists first theorized in the 1960s that a superfluid, a frictionless fluid with zero viscosity, could emerge within a crystal structure. That dual phase, known as a supersolid, was experimentally confirmed in ultracold atomic Bose-Einstein condensates in 2017. As highlighted in recent patent news and reported by Interesting Engineering, a joint team from the University of Warsaw, the Military University of Technology in Poland, the French National Center for Scientific Research (CNRS), and IBM Research Zurich has now produced this state at ambient temperatures.
The researchers relied on strong coupling between light and matter within an optical microcavity to generate exciton-polaritons, which are hybrid quasiparticles. Although these quasiparticles survive for only a few picoseconds, that brief window allows them to form a Bose-Einstein condensate that acts as a quantum superfluid.
“This is a textbook example of spontaneous symmetry breaking. Theory predicted that the supersolid could choose among several equivalent states, and that is exactly what we observed.”
— Guillaume Malpuech, professor at the Institut Pascal (CNRS)
Spontaneous symmetry breaking under laser excitation
To build the device, the researchers filled an optical microcavity with a custom liquid crystal and coated it with an organic semiconductor layer. Through this ingenious invention, when the superfluid transitions into a supersolid, it emits light displaying regularly spaced bright fringes. Every laser pulse directed at the experimental sample produced bright fringes at varying locations, confirming the transition.
The team recorded two distinct forms of spatial order at the same time, visible in polarization and in light intensity. Guillaume Malpuech, a professor at the Institut Pascal (CNRS), described the fringe variation as a textbook case of spontaneous symmetry breaking, noting that theory predicted the supersolid could select among multiple equivalent states.
Operational limits and electrical tunability up to 60°C
Fabricating and testing the system presented strict physical constraints because the organic semiconductor chemically reacted with the liquid crystal. Technicians at IBM Research Zurich deposited thin organic semiconductor films onto photonic structures manufactured by the Military University of Technology, requiring all measurements to conclude within a few hours of device assembly.
Unlike traditional setups that demand temperatures near absolute zero, the photonic structures remain functional in ambient warmth. Wiktor Piecek, a professor at the Military University of Technology, stated that the team's microcavities operate even at temperatures approaching 60°C. Because the device responds to an external electrical voltage, this scientific innovation provides a platform for controlling quantum phases in future quantum photonic hardware, an advance poised for future patent filing, according to findings published in the journal Science Advances.
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