The research work of the CNR with the University of Florence in collaboration with UCBM and Newcastle University
December 21, 2021 - While in our body the vortex dynamics favor the transfer of oxygen into the blood vessels and play a crucial role in the heart tissue, in classic fluids the vortex motion tends to disappear thanks to the diffusion of rotational energy. In the quantum world, however, vortices behave differently: the speed of their rotary motion cannot assume any value and the quantum nature of vortices influences the way in which they lose energy by interacting with each other. This dispersion can happen transforming rotational energy into sound waves in the quantum fluid. The study of this conversion mechanism is the subject of an intense multidisciplinary research activity, however made difficult by the complexity of ordinary materials in which inhomogeneities and imperfections prevent the'direct observation of this fundamental mechanism.
Technological advances in quantum simulation using ultracold atoms accelerate technological advances in vortex dynamics thanks to a new study: a group of researchers from theNational Institute of Optics of the Cnr at the Lens (European Laboratory of Non-Linear Spectroscopy) of theUniversity of Florence studied the dynamics of quantum vortices using a programmable simulator based on ultracold lithium atoms. This work, published in the prestigious magazine Nature, offers a new window on the elementary mechanisms underlying the relaxation of vortex quantum states such as turbulence, which still remain difficult to understand and model. The team of researchers, in collaboration with con theUniversità Campus Bio-Medico di Roma e with l'Newcastle University (UK), in particular observed for the first time the decay of quantum vortices into sound waves, in samples of lithium atoms cooled to temperatures close to absolute zero (-273 °C). "We have used innovative optical techniques to create an accelerator of quantum vortices, which are created in a controlled number and made to collide with a defined energy", explains Woojin Kwon, researcher of the Cnr-Ino at the Lens. "Our protocol is there'analogous at the atomic level of a particle accelerator: by introducing the vortices one by one into the atomic superfluid in a controlled manner, and observing their evolution over time, we were able to observe the generation of sound waves following the process of mutual annihilation between the vortices of circulation opposite (vortex and anti-vortex)”, keep it going Francesco Scazza, now professor at the University of Trieste and associated with Cnr-Ino.
"Our work represents a breakthrough for the understanding of the fundamental mechanisms of quantum vortex dynamics by linking to the experiments carried out on liquid helium samples, and offers new scenarios to studies on neutron saddles and high-temperature superconductors" continues Giacomo Roati, Cnr-Ino research manager at Lens and head of the research group.
"This work shows once again how quantum simulation with ultracold matter offers great potential for future investigations in different interdisciplinary research fields, from condensed matter to biological systems, with a completely new and extremely effective perspective", concludes Massimo Inguscio, professor emeritus atUniversità Campus Bio-Medico di Roma, past president of Cnr and head of the Research Area of Quantum Science and Technology at the Lens in Florence.
