Two natures in one: This is the extraordinary scenario that is unveiling with the study of the supersolid, a new state of matter that combines the properties of a superfluid (fluid without friction) with those of a solid (fixed and periodic structure of the particles). The super solid was created for the first time last autumn in a laboratory of the National Research Council (CNR) in Pisa, bringing a small sample of strongly magnetic atoms at very low temperatures, close to absolute zero. The new state of the matter is gaining great interest from the international scientific community, with the main European laboratories launched to study its properties. A team of researchers from Florence, Pisa and Trento has carried out a study of the motion of the supersolid that highlights for the first time the double nature of superfluid and solid.
The research was published in Nature and involves the Department of Physics and the European Laboratory of Nonlinear Spectroscopy (Lens) of the University of Florence, the National Institute of Optics of the National Research Council (CNR - INO, offices of Pisa and Trento) and the Department of Physics of the University of Trento [“Supersolid symmetry breaking from compressional oscillations in a dipolar quantum gas” Doi: 10.1038 / s41586-019-1568-6].
The study, which includes both experimental and theoretical aspects, demonstrates the peculiar nature of the supersolid, also confirming a general theory that links the symmetries of a physical system to the existence of sound waves within the system. The researchers applied a compression to the supersolid, as if it were a small spring, and studied its periodic oscillations. While ordinary solids and superfluids oscillate each with only one frequency, the supersolid oscillates simultaneously with two different frequencies. As the physicists of the University of Trento, Santo Roccuzzo, Alessio Recati and Sandro Stringari, who conducted the theoretical research explain, “To understand the experiment, one should to know that when a system is transformed breaking its own symmetry, a sound wave should appear. In our case, the two oscillation frequencies observed for the supersolid correspond precisely to two different sound waves, because the supersolid breaks simultaneously two symmetries being both superfluid and solid.”
Andrea Fioretti and Carlo Gabbanini, researchers of the CNR of Pisa comment: “Sound waves are the fundamental motion that is linked to all the other types of motion present in the material. So, there is a lot of anticipation in the scientific community: the supersolid is expected to combine general properties of solids and fluids previously considered incompatible.”
Just to give an example, researchers are interested in studying how the supersolid can withstand a load, as a solid normally does, while simultaneously sliding without friction like a superfluid. “Even if the supersolid made of ultracold atoms is a material that exists only in the laboratory at very low temperatures,” argue Luca Tanzi, Eleonora Lucioni and Giovanni Modugno of the University of Florence, “what teaches us can lead to the development of new materials and new technologies.”
