Ultracold quantum gases form crystalline and superfluid superbody

Superstrength is a paradoxical state when a substance crystallizes and at the same time becomes

superfluid.Predicted 50 years ago, such an illogical phase has been sought for a long time in superfluid helium. However, after decades of theoretical and experimental experiments and research, unequivocal proof of super-strength in these systems is still missing. Two research groups led by Francesca Ferlaino, one at the Institute of Experimental Physics at the University of Innsbruck and the other at the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, are now reporting the observation of signatures of this exotic ultracold state in quantum gases.

UNI INNSBRUCK

Although most of the work so far has beenfocused on helium, researchers have recently turned to quantum gases—in particular, those that have strong dipole interactions. “Recent experiments have shown that such gases have a fundamental similarity to superfluid helium,” says Lorian Chomaz, referring to experimental advances in Innsbruck and Stuttgart over the past few years. “These features lay the groundwork for achieving a state where several tens of thousands of gas particles spontaneously organize into a self-defining crystalline structure while sharing the same macroscopic wave function—the hallmarks of superhardness.”

Researchers in Innsbruck experimentally createdstates that demonstrate these characteristics of super-strength, tuning the force of interaction between particles in quantum gases of both erbium and dysprosium. “While in erbium the superhard state is only temporary, our realization of dysprosium demonstrates unprecedented stability,” says Francesca Ferlayno. "Overstretched behavior not only lasts a long time, but is also directly achieved by evaporative cooling, starting with a thermal sample."