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Séminaire « Magnétisme et Physique du spin » de l’INSP

Combining spin resolution with femto- and attosecond time resolution in photoemission - Mauro Fanciulli - Mardi 17 novembre 2020 à 11 h

En visioconférence

Mauro Fanciulli - Laboratoire de Physique des Matériaux et Surfaces, CY Cergy Paris Université - Laboratoire d’Interactions, DYnamiques et Lasers, CEA Saclay

Abstract

For a complete understanding of the photoemission process, in addition to the energy and angular distribution of photoelectrons also their spin polarization and their dynamics at different time scales need to be considered. In the first part of the seminar I will show how the study of spin polarization in spin-degenerate systems can lead to fundamental results, since it can be indirectly related to the attosecond (e-18 s) time scale of the photoemission process thanks to a common link in the transition matrix elements. In the second part, I will present the photoemission setup we recently installed at the Attolab SE10 beamline, a high harmonics generation (HHG) laser source which can operate in two modes. One allows to perform reconstruction of attosecond beating by interference of two-photon-transitions (RABBIT) experiments to directly access the attosecond time scale. The second mode operates in the femtosecond regime, allowing for a complete spin-, time- and angle-resolved photoemission spectroscopy (STARPES) experiment. In the third part I will present our first STARPES results obtained on the type-II Weyl semimetal candidate WTe2. Comparison with fully relativistic calculations allows us to observe a spin accumulation above the Weyl points region, that is consistent with a spin-selective bottleneck effect in this topological material.