2019 EPFL doctorate Award - Finalist – Mauro Fanciulli
Special distinction from the selection committee to Mauro Fanciulli for his thesis “Spin polarization and attosecond time delay in photoemission from solids”
EPFL thesis n°8469 (2018)
Thesis director: Prof. J. H. Dil
Photoemission is a quantum process where a solid illuminated by UV light emits electrons. The measurement of their properties such as energy, momentum and spin polarization allows to reconstruct their behaviour inside the solid.
It is not always possible to determine the electronic properties of the solid in its initial state, since the outcome of a measurement is influenced by the particular choice of parameters in the experiment. However, it is possible to exploit this fact in order to understand something about the process itself: in particular, to learn about the ultra-fast time scale of the emission, since it can be related to the spin polarization.
I developed and explored the limits of the analytical model that allows to indirectly estimate the time scale from the measurement of the spin polarization, without experimental time resolution. Furthermore, I performed experiments for two samples: a copper single crystal and a high-temperature cuprate superconductor. The results are in the attosecond (10^-18 seconds) domain, which is the fundamental time scale at the atomic level.
In general, my work contributes to the understandings of the photoemission process and shows a new way to access ultra-fast time scales in quantum mechanics.