Ferlaino's group at the University of Innsbruck have made a groundbreaking discovery by experimentally confirming the precence of vortices in supersolids, a unique phase of matter that exhibits both solid and superfluid properties. This discovery opens new possibilities for studying laboratory analogues of rotating neutron stars.
Supersolids behave like a superfluid with zero viscosity, while maintaining a solid's crystalline structure. Initially observed in 2019, they display density patterns resembling mountains and valleys. Until now, one key feature—vortex formation—had remained elusive. The Innsbruck team has now detected these vortices by observing density holes in a cloud of ultracold dysprosium atoms. Their findings were confirmed by a new experimental setup using a "magnetostirring" method to rotate the supersolid and observe vortex patterns.The team used a rotating magnetic field to control the interactions between atoms, causing them to form a supersolid. When the rotation speed exceeded a certain threshold, vortices appeared in the low-density valleys of the supersolid. In contrast, vortices in superfluids formed only at much higher rotation rates. This helps to explain why vortices form more easily in supersolids, where the low-density regions offer less resistance.
These vortices, while seemingly paradoxical in a crystal-like structure, suggest that the lattice is not rigid, but flexible enough to allow for superfluid behavior. The new experiment provides a valuable window for further studies on supersolids, with potential implications for understanding neutron stars, where a similar supersolid layer might exist.
References
E. Casotti, “Observation of vortices in a dipolar supersolid,” Nature 635, 327 (2024).
S. B. Prasad et al., “Vortex lattice formation in dipolar Bose-Einstein condensates via rotation of the polarization,” Phys. Rev. A 100, 023625 (2019).
G. Biagioni et al., “Measurement of the superfluid fraction of a supersolid by Josephson effect,” Nature 629, 773 (2024).