Spin-dipole oscillation and relaxation of coherently coupled Bose-Einstein condensates

Year: 2015

Authors: Sartori A., Marino J., Stringari S., Recati A.

Autors Affiliation: INO-CNR BEC Center and Dipartimento di Fisica, Universita` di Trento, 38123 Povo, Italy; Institute of Theoretical Physics, TU Dresden, D-01062 Dresden, Germany; Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany

Abstract: We study the static and the dynamic response of coherently coupled two component Bose-Einstein condensates due to a spin-dipole perturbation. The static dipole susceptibility is determined and is shown to be a key quantity to identify the second order ferromagnetic transition occurring at large inter-species interaction. The dynamics, which is obtained by quenching the spin-dipole perturbation, is very much affected by the system being paramagnetic or ferromagnetic and by the correlation between the motional and the internal degrees of freedom. In the paramagnetic phase the gas exhibits well defined out-of-phase dipole oscillations, whose frequency can be related to the susceptibility of the system using a sum rule approach. In particular in the interaction SU(2) symmetric case, i.e., all the two-body interactions are the same, the external dipole oscillation coincides with the internal Rabi flipping frequency. In the ferromagnetic case, where linear response theory in not applicable, the system shows highly non-linear dynamics. In particular we observe phenomena related to ground state selection: the gas, initially trapped in a domain wall configuration, reaches a final state corresponding to the magnetic ground state plus small density ripples. Interestingly, the time during which the gas is unable to escape from its initial configuration is found to be proportional to the square root of the wall surface tension.


Volume: 17      Pages from: 093036-1  to: 093036-11

More Information: AR acknowledges useful discussions with Marta Abad, Markus Heyl, Nicolas Pavloff and Wilhelm Zwerger, and support from the Alexander von Humboldt foundation. A.S. acknowledges Komet 337 group of their Johannes Gutenberg Universitat Mainz for their kind hospitality. This work has been supported by ERC through the QGBE grant and by Provincia Autonoma di Trento.
KeyWords: coherently coupled Bose-Einstein condens; paramagnetic-ferromagnetic transition; collective modes; spin-dipole dynamics; spinor order parameter
DOI: 10.1088/1367-2630/17/9/093036

Citations: 22
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