A team of researchers from the University of Florence and Cnr Ino, led by Leonardo Fallani, has recreated in the laboratory a system that has made it possible to “see” for the first time how the current is bent by the magnetic field, in a regime of strong interaction among charges never previously studied.

The results of the experiment, carried out as part of the ERC Consolidator Grant TOPSIM research project of which Fallani is scientific director, have been published in the prestigious journal Science: during the experiment, carried out in the laboratories of the Department of Physics and Astronomy of the The European Laboratory of Nonlinear Spectroscopy (LENS), the National Institute of Optics (Ino) of the Cnr and the universities of Geneva and Grenoble have collaborated with the Florence studios.

The experimental system developed in Florence is a quantum simulator, i.e. a “dedicated” quantum computer, designed with the aim of reproducing the quantum effect of interest. The results are extremely promising for studying the microscopic origin of the quantization of the Hall effect, which – 40 years after its discovery – is still looking for a complete theoretical interpretation.

The Hall effect is a physical phenomenon according to which, when an electric current flows inside a material in the presence of a magnetic field, instead of moving in a straight line, it “bends” and gives rise to an accumulation of electric charges at the edges. This effect is the basis of widespread techniques for the characterization of materials and is used in the most common devices for measuring magnetic fields, such as those found in our mobile phones.

Instead of working with conventional materials, the experimental team managed to recreate a “prototype” of material in the laboratory where neutral atoms, cooled to a few billionths of a degree above absolute zero, play the role of electrons.

By manipulating atoms with laser light, the researchers were able to make them behave like charged particles in the presence of an “artificial” magnetic field and to observe precisely how atomic trajectories were bent by the magnetic field. For the first time the Hall effect has been measured as the interactions between particles vary, confirming the theoretical predictions of researchers from the Universities of Geneva and Grenoble, led by Thierry Giamarchi and Michele Filippone, involved in the conception of the experiment and in the interpretation of the results.

This research will also be carried out in the context of the PNRR initiatives dedicated to the development of new quantum technologies – Fallani coordinates the participation of Unifi in the new extended partnership National Quantum Science and Technology Institute – and of important Cnr-Ino projects of the Quantum Flagship.

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