An international team of physicists has transformed laser light into a supersolid, marking an entirely new process for achieving this mysterious state of matter.
On the quantum level, matter often exhibits strange behaviors, and the supersolid state is one of the most counterintuitive examples. In this state, atoms arrange into a crystal lattice like a solid but also flow without friction, a property typically associated with liquids.
The Quest to Understand Supersolids
Scientists first proposed the idea of a solid that could demonstrate fluid-like flow in the 1960s, with theoretical exploration intensifying in the 1970s.
Helium was initially considered the most promising candidate for achieving this exotic phase of matter. However, early experiments attempting to produce a solid with superfluid properties yielded disappointing results. In the 1980s, physicist John Goodkind used ultrasound techniques to identify anomalies in matter that suggested supersolids might be feasible.
By the 2000s, new experimental data provided stronger hints of supersolid behavior, though some findings conflicted with theoretical predictions, making the state even more elusive.
Creating a Supersolid With Laser Light
For decades, researchers believed that achieving a supersolid state required ultracold atomic Bose-Einstein condensates combined with electromagnetic fields. This method, which was only successfully demonstrated in recent years, produced a material structured like table salt but also capable of flowing.
The latest research, however, takes an entirely different approach, creating a supersolid without using atoms at all.
The team began with a piece of gallium oxide designed with precise ridges to interact with an incoming laser beam. When the laser light struck the semiconductor’s ridges, it produced a quasiparticle known as a polariton. The shape of the ridges then constrained the polariton’s motion, forcing it into a supersolid state.
Confirming the Supersolid State
Proving their achievement was a challenge, as no experiment had ever produced a supersolid using light before. However, the team successfully demonstrated both the solid and fluid properties of their laser-generated supersolid, confirming that it had zero viscosity.
To validate their results, researchers used wave interference techniques to image the polariton’s state, allowing them to record the microscopic spatial coherence of the quasiparticles. Their data provided concrete proof of the quasiparticles’ local and long-range order, confirming the formation of a supersolid.
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Additionally, optical data allowed them to measure the entire wave function, offering unprecedented insights into the behavior of the supersolid.
Future Research and Applications
The research team plans to continue investigating the structure of their newly created supersolid, focusing on engineering its crystalline structure for further study. They suggest that because their supersolid is made of light, it may be more flexible and easier to manipulate than atomic supersolids, making this platform a fundamentally different and promising avenue for future research.
The paper “Emerging Supersolidity in Photonic-crystal Polariton Condensates” appeared on March 5, 2025 in Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted atryan@thedebrief.org, and follow him on Twitter@mdntwvlf.