Two-dimensional supersolidity in a dipolar quantum gas

• Published in: Nature (London) Vol. 596; no. 7872; pp. 357 - 361
• Main Authors: Norcia, Matthew A., Politi, Claudia, Klaus, Lauritz, Poli, Elena, Sohmen, Maximilian, Mark, Manfred J., Bisset, Russell N., Santos, Luis, Ferlaino, Francesca
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.08.2021; Nature Publishing Group
• Subjects: 639/766/119/2791; 639/766/119/2795; 639/766/36/1125; 639/766/483/3924; Arrays; Condensed matter; Dysprosium; Experiments; Fluids; Gases; Helium; Humanities and Social Sciences; Magnetic fields; multidisciplinary; Particle density (concentration); Phase transitions; Properties; Quantum theory; Science; Science (multidisciplinary); Solid helium; Superfluidity; Austria
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-021-03725-7

Supersolid states simultaneously feature properties typically associated with a solid and with a superfluid. Like a solid, they possess crystalline order, manifesting as a periodic modulation of the particle density; but unlike a typical solid, they also have superfluid properties, resulting from coherent particle delocalization across the system. Such states were initially envisioned in the context of bulk solid helium, as a possible answer to the question of whether a solid could have superfluid properties 1 – 5 . Although supersolidity has not been observed in solid helium (despite much effort) 6 , ultracold atomic gases provide an alternative approach, recently enabling the observation and study of supersolids with dipolar atoms 7 – 16 . However, unlike the proposed phenomena in helium, these gaseous systems have so far only shown supersolidity along a single direction. Here we demonstrate the extension of supersolid properties into two dimensions by preparing a supersolid quantum gas of dysprosium atoms on both sides of a structural phase transition similar to those occurring in ionic chains 17 – 20 , quantum wires 21 , 22 and theoretically in chains of individual dipolar particles 23 , 24 . This opens the possibility of studying rich excitation properties 25 – 28 , including vortex formation 29 – 31 , and ground-state phases with varied geometrical structure 7 , 32 in a highly flexible and controllable system. Two-dimensional supersolidity is demonstrated using highly magnetic, ultracold dysprosium atoms.