Dynamics of a trapped Bose-Einstein condensate in the presence of a one-dimensional optical lattice

Year: 2003

Authors: Cataliotti F.S., Fallani L., Ferlaino F., Fort C., Maddaloni P., Inguscio M.

Autors Affiliation: LENS, Dipartimento di Fisica, Universit`a di Firenze and Istituto Nazionale per la Fisica della
Materia, via Nello Carrara 1, I-50019 Sesto Fiorentino (Firenze), Italy

Abstract: We explore the dynamics of a Bose–Einstein condensate created in the
combined potential of a far-detuned laser standing wave superimposed to a
3D harmonic magnetic potential.
We report the investigation of low-lying collective modes showing that
the macroscopic dynamics along the optical lattice is strongly modified,
resulting in a shift of the dipole and quadrupole mode frequencies depending
on the height of the optical lattice, whereas the transverse breathing mode,
occurring perpendicularly to the lattice axis, is not perturbed. The
experimental findings are compared with the theoretical treatment that
generalizes the hydrodynamic equation of superfluids for a weakly
interacting Bose gas to include the effects of the periodic potential.
We show that the array of condensates trapped in the optical wells and
driven by the harmonic magnetic potential is equivalent to an array of
Josephson junctions. In the regime of ‘small’ amplitude dipole oscillation
the system performs a collective motion and we investigate the
current–phase dynamics measuring the critical Josephson current.
Increasing the amplitude of the dipole oscillation, we observe a transition
from the coherent oscillation (superfluid regime) to a localization of the
condensates in the harmonic trap (‘insulator’ regime). The onset of the
coherent regime breakdown is interpreted as the result of a discrete
modulational instability occurring when the velocity of the centre of mass of
the system is larger than a critical velocity proportional to the tunnelling rate
between adjacent wells.

Journal/Review: JOURNAL OF OPTICS B-QUANTUM AND SEMICLASSICAL OPTICS

Volume: 5 (2)      Pages from: S17  to: S22

KeyWords: Bose-Einstein condensation; Collective excitation; Josephson effect; Periodic potential; Oscillations; Quantum optics; Three dimensional; Velocity; Bose gas; Bose-Einstein condensate; Harmonic trap; Josephson current; Optical lattice, Gas condensates
DOI: 10.1088/1464-4266/5/2/353

Citations: 12
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