A paradoxical material that is both a solid and a liquid can start rotating on its own without being stirred.
April 23, 2026
Original Paper
Supersolid Rotation in an Annular Bose-Einstein Condensate coupled to a Ring Cavity
arXiv · 2604.16573
The Takeaway
Supersolids are a bizarre state of matter that maintain a rigid crystal structure while allowing atoms to flow without friction. This theoretical model shows that a supersolid confined to a ring can spontaneously start spinning due to its interaction with a light cavity. No physical force or stirring is required to kickstart this motion. This behavior breaks the standard understanding of how objects begin to rotate in a vacuum. Mastering this self-spinning matter could help physicists design ultra-precise sensors for measuring gravity or the rotation of the Earth.
From the abstract
We theoretically investigate an annularly confined Bose-Einstein Condensate (BEC) coupled to a four-mirror ring cavity supporting traveling-wave optical modes. Under symmetric driving by counter-propagating Laguerre-Gaussian beams carrying equal and opposite orbital angular momenta, the system realizes supersolid phases coexisting with persistent superfluid circulation. Specifically, we obtain a supersolid state if we start with a BEC of winding number $L_p$ as well as supersolid packets with co