Ricerc@Sapienza

The proposers have recently demonstrated the existence of a new mesoscopic phase in nanodisordered ferroelectrics known as a super-crystal. The super-crystal is characterized by unique and unexpected properties, such as binary birefringence and giant broadband refraction. These are accompanied by a strongly enhanced optical nonlinearity that has allowed the proposers to study numerous new scenarios in nonlinear wave physics, these including the observation of replica-symmetry-breaking in waves, Fermi-Pasta-Ulam-Tsingou recurrences, along with more speculative rogue waves. The FRACFER proposal aims at experimentally exploring ferroelectric cluster percolation during a structural transition. Using giant broadband optical refraction, we will use 3D orthographic projection imaging in ferroelectric KTN:Li to provide, for the first time, direct imaging evidence of self-similar fractal percolation.
The basic goals of the project are
G.I) demonstrate direct cluster imaging in the volume using crossed-polarizer experiments in a super-crystal;
G.II) collect dynamical data on ferroelectric cluster dynamics under the influence of external control parameters, these including temperature and bias static electric fields;
G.III) determine the percolation thresholds, critical parameters and fractal dimension of the percolative chain.
In FRACFER, focus is on the experimental study of the alteration in the structure of a ferroelectric super-crystal leading to its ultimate breakdown. Experiments will be carried out in solid-solutions of KTN:Li (potassium-lithium-tantalate-niobate).
Key expected outcomes of FRACFER are:
O.I) the determination of the fractal dimension of cluster percolation during the breakdown of a ferroelectric super-crystal through direct-imaging;
O.II) the elaboration of a physical model that connects fractal percolation to the susceptibility of the topologically dominated structure of a ferroelectric super-crystal.