.. Istituto Nazionale di Ottica
Bose-Einstein Condensation
Trento, Italy

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Experiments with ultracold atoms

 


LAB TEAM

Principal investigators: Gabriele Ferrari, Giacomo Lamporesi.
Postdoc: Tom Bienaimé.
PhD students: Simone Serafini, Eleonora Fava, Giacomo Colzi, Carmelo Mordini, Matteo Barbiero.

Former students PhD thesis:
Simone Donadello (2016) "Observation of the Kibble-Zurek mechanism in a bosonic gas".  


 

RECENT RESULTS

Vortex dynamics in cigar-shaped BECs

Single vortices in elongated condensates are mainly oriented along a radial direction and tend to precess around elliptical orbits around the center. We track their dynamics by performing a real-time weakly destructive imaging. The measured period verifies the predicted dependence on the local chemical potential. We also see signatures of different ways of interaction among approaching vortices.

Reference:
Dynamics and Interaction of Vortex Lines in an Elongated Bose-Einstein Condensate
S.Serafini, M. Barbiero, M. Debortoli, S. Donadello, F. Larcher, F. Dalfovo, G. Lamporesi, G. Ferrari,
arXiv:1507.01511, Phys. Rev. Lett. 115, 170402 (2015)

Real-time tracking of the axial vortex position while precessing around the center of the BEC. Single vortex, two noninteracting, two interacting and many vortices are shown.
 

Solitonic vortices

The geometrical properties of a system have an influence on the nature of defects that can be supported. Besides common solitons in quasi 1D systems and vortices in round pancake like condensates, we observed solitonic vortices in elongated samples. These hybrid defects are vortices aligned along a short axis with a 2pi phase winding, but also show a planar density depletion in the radial plane containing the vortex.

References:
Observation of Solitonic Vortices in Bose-Einstein Condensates
S. Donadello, S. Serafini, M. Tylutki, L.P. Pitaevskii, F. Dalfovo, G. Lamporesi, G. Ferrari,
arXiv:1404.4237, Phys. Rev. Lett. 113, 065302 (2014) (see also Physics Viewpoint)


Solitonic Vortices in Bose-Einstein Condensates
M. Tylutki, S. Donadello, S. Serafini, L.P. Pitaevskii, F. Dalfovo, G. Lamporesi, G. Ferrari,
arXiv:1410.5475, Eur. Phys. J. Special Topics 224, 473-475 (2015)


Tri-axial absorption imaging of elongated BECs after a long time of flight providing clear signatures of the presence of solitonic vortices with opposite circulation.
 

Spontaneous generation of defects

Quantum criticalities are mechanisms driving disparate phenomena ranging from the origin of our universe to the appearance of defects in uniform systems. We use ultracold atoms at the BEC transition to explore the Kibble-Zurek mechanism by directly observing the creation of phase defects in the order parameter of a Bose-Einstein condensate for temperature quenched BECs of sodium atoms.

Reference:
Spontaneous creation of Kibble-Zurek solitons in a Bose-Einstein condensate
G. Lamporesi, S. Donadello, S. Serafini, F. Dalfovo, G. Ferrari,
arXiv:1306.4523, Nat. Phys. 9, 656 (2013)


A condensate of Sodium atoms is formed by quenching the temperature across the BEC phase transition. If the quench is fast, defects appear in the order parameter due to the Kibble-Zurek mechanism.
 


 

COOLING TECHNIQUES

Gray Molasses cooling

We implemented a gray molasses cooling technique on a sodium precooled sample by using blue-detuned light on the D1 transition. Starting from a gas of 3x109 atoms at 350 microK our gray molasses stage allows to obtain a more degenerate sample containing 2x109 atoms at 9 microK. The final PSD is 10-4, one order of magnitude higher than the best we obtained with a molasses stage using the D2 transition.

Reference: Sub-Doppler cooling of sodium atoms in gray molasses
G. Colzi, G. Durastante, E. Fava, S. Serafini, G. Lamporesi and G. Ferrari,
arxiv:1512.07053, Phys. Rev. A 93, 023421 (2016)

Compact atomic source

We realized a novel, multi-species, compact cold atomic source. Permanent magnets are used to create a 2D quadrupole magnetic field for a 2D-MOT. Their residual field in combination with a vertical laser beam form a compact Zeeman slower that enhances the number of trappable atoms. Eventually cooled atoms are pushed along the 2D-MOT axis towards a 3D-MOT cleaner chamber. This geometry also avoids hot atoms from the source to directly reach the 3D-MOT.

Reference: A compact high-flux source of cold sodium atoms
G. Lamporesi, S. Donadello, S. Serafini, and G. Ferrari,
arXiv:1301.6566, Rev. Sci. Instrum. 84, 063102 (2013)


Scheme of the multi-species compact cold atom source.
 


 

PROJECTS

Spin-Orbit coupled Bose gases

Defects in spinor condensates