Presentation

My name is Federico Cilento and I conduct my experimental research activity at the T-ReX Laboratory, within the Fermi@Elettra project. As the name suggests, the T-ReX Lab. is intended to exploit time-resolved techniques in general, to study the physical properties of complex phases of matter of novel materials.

In particular, spectroscopic techniques are the ideal candidates to succeed in this complex task. Among these, optical and photoemission spectroscopies are the ideal candidates, given their capability of accessing the microscopic properties of materials. In fact, they allow to measure and reveal the dielectric function and directly the electronic band structure of a given material, respectively.

In this respect, by performing a time-resolved experiment based on ultrashort (~100 fs), coherent laser pulses, many new insights can be gained. The basic principle of ‘time-resolved’ is simple: a first pulse (called pump) prepares the system in an excited, out-of-equilibrium state, while a subsequent pulse (called probe) probes how the optical or electronic properties are modified in the excited transient state. It is a (almost) straightforward task to turn an equilibrium optical or photoemission experiment into a non-equilibrium, time resolved fashion. Less obvious is the rich amount of information that can be learnt. In details, by time-resolved optical spectroscopy, the evolution on ultrafast timescales of the dielectric function of a material can be measured, providing fundamental information about the degrees of freedom of the system which have been excited. Complementary, time-resolved angular resolved photoemission spectroscopy can visualize in realtime how the angular resolved electronic band structure is modified when the system is perturbed.

The power of a time-resolved approach stands in the fact that it allows to unravel the subtle interplay between different and often intertwined electronic or phononic degrees of freedom or collective excitations of a system, thanks to their different characteristic timescales and spectral features, in different temperature-doping conditions within the phase diagram of a complex material.

Developing and exploiting techniques combining both the temporal and the spectral-energetic-momentum resolutions is fundamental to explore the physics of strongly correlated materials. Moreover, the development of a well-suited interpretative framework is of paramount importance. The combination of experiment and theory regarding the out-of-equilibrium physics is to my experience one of the more promising route to get advances in the field of strongly correlated electronic materials, such as transition-metal oxides, cuprate superconductors and iron-based superconductors.

Along these lines develops my present and future research activity, based on the application of time-resolved angular resolved photoemission spectroscopy to the study of high-temperature superconductivity in copper and iron based superconductors.