Time-resolved optical spectroscopies (tr-OS) are powerful tools to investigate how materials respond to light on ultrafast timescales. By using femtosecond laser pulses, these techniques capture the evolution of electronic and lattice degrees of freedom in real time, providing a unique window into the microscopic processes that govern conductivity, magnetism, and optical properties. Unlike static measurements, tr-OS reveals how new states of matter emerge dynamically, when materials are driven far from equilibrium by intense light excitation.

Among the various tr-OS approaches, in our UPHOS laboratory at the Physics Department, we employ time-resolved reflectivity and magneto-optic Kerr and Faraday effects to probe the role of electronic correlations and spin interactions in establishing novel quantum phases. By tracking the temporal dynamics of these optical signals, we can unveil the physical origin of phase transitions and disentangle the contributions of quasiparticles, collective excitations to the emergence of exotic charge-ordered states, and new magnetic ground states.

Within this framework, the project will focus on the development and characterization of a versatile experimental setup, capable of combining multiple tr-OS at one place. The candidate will contribute to the optimization of the setup based on a state-of-the-art ultrafast laser source that drives a non-linear optical parametric amplifier (NOPA) capable to deliver pulses shorter than 30 fs (1 fs = 10^-15s), that are used to investigate the materials response at cryogenic temperatures. The ultimate goal is to unravel the photo-induced dynamics of collective excitations in multiferroic systems, a wide class of materials displaying simultaneous charge and spin long-range orders, and to disentangle their mutual interactions on the electron-electron and electron-spin timescales.

The project is highly interdisciplinary, bridging the curricula in Photonic and Quantum Technologies with Quantum Materials and Nanophysics. The candidate will gain hands-on expertise in ultrafast optics, nonlinear processes, cryogenic techniques, and data acquisition/analysis. Working within our international research network, the student will acquire both technical skills and a strong scientific perspective, taking the first steps into academic research at the frontier of light–matter interaction.

Contacts: ettore.carpene@polimi.it, alberto.crepaldi@polimi.it, claudia.dallera@polimi.it