Ultracold quantum gases form crystalline and superfluid superbody

Overstrength is a paradoxical state when a substance crystallizes and becomes

superfluid. Predicted 50 years ago, such an illogical phase was searched for a long time in superfluid helium. However, after decades of theoretical and experimental experiments and research, unequivocal proof of the presence of superstrength 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 of Quantum Optics and Quantum Information of the Austrian Academy of Sciences, are currently reporting on signs of this exotic state in the ultracold state of quantum gases.


Although so far most of the work 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 the experimental advances in Innsbruck and Stuttgart over the past few years. "These features lay the foundation for achieving a state where several tens of thousands of gas particles spontaneously organize themselves into a self-determining crystal structure, while at the same time sharing the same macroscopic wave function - the distinguishing features 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."