Giacomo Lamporesi

Spontaneous creation of Kibble–Zurek solitons in a Bose–Einstein condensate

The Kibble–Zurek mechanism describes the spontaneous formation of defects in systems that are undergoing a second-order phase transition at a finite rate. Familiar to cosmologists and condensed matter physicists, this mechanism is now found to be responsible for the spontaneous creation of solitons in a Bose–Einstein condensate.

Observation of Solitonic Vortices in Bose-Einstein Condensates

We observe solitonic vortices in an atomic Bose-Einstein condensate (BEC) after free expansion. Clear signatures of the nature of such defects are the twisted planar density depletion around the vortex line, observed in absorption images, and the double dislocation in the interference pattern obtained through homodyne techniques. Both methods allow us to determine the sign of the quantized circulation. Experimental observations agree with numerical simulations. These solitonic vortices are the decay product of phase defects of the BEC order parameter spontaneously created after a rapid quench across the BEC transition in a cigar-shaped harmonic trap and are shown to have a very long lifetime.

Vortex reconnections and rebounds in trapped atomic Bose-Einstein condensates

Understanding interactions between filamentary structures could offer important insights into the dynamics of a wide range of physical systems. A new imaging technique reveals novel vortex filament interactions in a Bose-Einstein condensate (BEC) and helps establish BECs as a powerful laboratory for investigating filament dynamics.

Dynamics and Interaction of Vortex Lines in an Elongated Bose-Einstein Condensate.

We study the real-time dynamics of vortices in a large elongated Bose-Einstein condensate (BEC) of sodium atoms using a stroboscopic technique. Vortices are produced via the Kibble-Zurek mechanism in a quench across the BEC transition and they slowly precess keeping their orientation perpendicular to the long axis of the trap as expected for solitonic vortices in a highly anisotropic condensate. Good agreement with theoretical predictions is found for the precession period as a function of the orbit amplitude and the number of condensed atoms. In configurations with two or more vortices, we see signatures of vortex-vortex interaction in the shape and visibility of the orbits. In addition, when more than two vortices are present, their decay is faster than the thermal decay observed for one or two vortices. The possible role of vortex reconnection processes is discussed.

Compact high-flux source of cold sodium atoms.

We present a compact source of cold sodium atoms suitable for the production of quantum degenerate gases and versatile for a multi-species experiment. The magnetic field produced by permanent magnets allows to simultaneously realize a Zeeman slower and a two-dimensional magneto-optical trap (MOT) within an order of magnitude smaller length than standard sodium sources. We achieve an atomic flux exceeding 4 × 10(9) atoms/s loaded in a MOT, with a most probable longitudinal velocity of 20 m/s, and a brightness larger than 2.5 × 10(12) atoms/s/sr. This atomic source allows us to produce pure Bose-Einstein condensates with more than 10(7) atoms and a background pressure limited lifetime of 5 min.

Sub-Doppler cooling of sodium atoms in gray molasses

We report on the realization of sub-Doppler laser cooling of sodium atoms in gray molasses using the D1 optical transition (

Spin-dipole oscillation and polarizability of a binary Bose-Einstein condensate near the miscible-immiscible phase transition

3s\, ^2S_{1/2} \rightarrow 3p\, ^2P_{1/2}

Creation and counting of defects in a temperature-quenched Bose-Einstein condensate

) at 589.8 nm. The technique is applied to samples containing

Observation of a spinning top in a Bose-Einstein condensate

3\times10^9

Dynamical equilibration across a quenched phase transition in a trapped quantum gas

atoms, previously cooled to 350