Thèse présentée par Rishabh Sharma pour obtenir le grade de
Docteur en Physique de l’Université Sorbonne Paris Nord
I will present the work I have done during the three years of my doctoral thesis on the Rubidium experiment within the BEC group. During my thesis we studied the Melting scenario of a vortex lattice in a quasi-2D superfluid rotating at the bottom of the bubble-shaped trap. The presence of this fusion scenario in 2D crystals is well explained by the theory of Kosterlitz, Thouless, Helperin, Nelson and Young (KTHNY). We have shown the presence of the transition from the hexatic phase to the liquid phase as a function of the increase in the rotation frequency. I will also present the various modifications that were made during my thesis such as the installation of a new dipole trap detuned towards red (1064nm) at the place of the old plug trap (532nm) which was detuned towards blue, in order to limit the excitations of the center of mass motion of the atoms during their transfer into the bubble trap from the dipole trap. I will also present the installation of a new laser chain in our experiment which was set up to implement a new non-destructive imaging method that allows us to take several in situ images of a superfluid during the experimental sequence unlike one image per sequence with an standard absorption imaging method. This method will allow us in the future to study the temporal dynamics of a superfluid in the same experimental conditions.
Jury Member:
Thomas BOURDEL, Laboratoire Charles Fabry (Institut d’Optique, Palaiseau), Rapporteur
Kali WILSON, University of Strathclyde, Rapporteuse
Jacob REICHEL, Laboratoire Kastler Brossel (Paris,), Examinateur
Giacomo ROATI, LENS – European Laboratory for Non-Linear- Spectrocopy (Italie), Examinateur
Athanasios LALIOTIS, Laboratoire de Physique des Lasers, Université Sorbonne Paris Nord, Examinateur
Romain DUBESSY, Aix-Marseille Université (AMU), Co-directeur de thèse
Hélène PERRIN, Laboratoire de Physique des Lasers, Université Sorbonne Paris Nord, Directrice de thèse
Keywords: Bose-Einstein condensate, adiabatic potentials, vortex lattice, fast rotations, quasi-2D superfluid.
Soutenance: Le 31 Janvier 2025 à 14h00