Quantum liquid becomes solid when heated

Newswise —

Supersolids represent a thrilling and novel field of investigation that showcases dual solid and superfluid characteristics. In 2019, the conclusive demonstration of this state was achieved for the first time in ultracold quantum gases by three research teams, including the group headed by Francesca Ferlaino at the Department of Experimental Physics at the University of Innsbruck and the ÖAW Institute for Quantum Optics and Quantum Information (IQOQI) in Innsbruck.

Claudia Politi, a member of Francesca Ferlaino's team, reported in 2021 that their team meticulously examined the life cycle of supersolid states within a dysprosium atom dipolar gas. During their study, they discovered an unexpected phenomenon: "Our findings indicated that an escalation in temperature encourages the development of supersolid structures," notes Politi. "This unforeseen behavior provided a significant stimulus to the theoretical framework, which had previously disregarded thermal fluctuations in this context."

The researchers at Innsbruck, in collaboration with the Danish theoretical group led by Thomas Pohl, teamed up to investigate the impact of thermal fluctuations. They devised and published a theoretical model in Nature Communications that clarifies the experimental findings and supports the hypothesis that heating the quantum liquid can trigger the emergence of a quantum crystal. According to the theoretical model, these structures can form more effortlessly as the temperature increases.

Francesca Ferlaino expressed her enthusiasm, stating that "With the help of the new model, we now possess a phase diagram that demonstrates the emergence of a supersolid state as a temperature-dependent function." She further explains, "The anomalous behavior, which goes against our everyday experience, can be attributed to the anisotropic character of the dipole-dipole interaction of the highly magnetic dysprosium atoms."

This research represents a crucial stride towards enhanced comprehension of the supersolid states of matter, and was supported by numerous organizations, including the Austrian Science Fund FWF, the European Research Council ERC, and the European Union.

Publication: Heating a quantum dipolar fluid into a solid. J. Sanchez-Baena, Claudia Politi, F. Maucher, Francesca Ferlaino, and T. Pohl. Nature Communications 14, 1868 (2023) DOI: https://doi.org/10.1038/s41467-023-37207-3