Collective excitation frequencies and stationary states of trapped dipolar Bose-Einstein condensates in the Thomas-Fermi regime
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)
- School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia)
We present a general method for obtaining the exact static solutions and collective excitation frequencies of a trapped Bose-Einstein condensate (BEC) with dipolar atomic interactions in the Thomas-Fermi regime. The method incorporates analytic expressions for the dipolar potential of an arbitrary polynomial density profile, thereby reducing the problem of handling nonlocal dipolar interactions to the solution of algebraic equations. We comprehensively map out the static solutions and excitation modes, including non-cylindrically-symmetric traps, and also the case of negative scattering length where dipolar interactions stabilize an otherwise unstable condensate. The dynamical stability of the excitation modes gives insight into the onset of collapse of a dipolar BEC. We find that global collapse is consistently mediated by an anisotropic quadrupolar collective mode, although there are two trapping regimes in which the BEC is stable against quadrupole fluctuations even as the ratio of the dipolar to s-wave interactions becomes infinite. Motivated by the possibility of a fragmented condensate in a dipolar Bose gas due to the partially attractive interactions, we pay special attention to the scissors modes, which can provide a signature of superfluidity, and identify a long-range restoring force which is peculiar to dipolar systems. As part of the supporting material for this paper we provide the computer program used to make the calculations, including a graphical user interface.
- OSTI ID:
- 21450613
- Journal Information:
- Physical Review. A, Vol. 82, Issue 3; Other Information: DOI: 10.1103/PhysRevA.82.033612; (c) 2010 The American Physical Society; ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
ANISOTROPY
BOSE-EINSTEIN CONDENSATION
BOSE-EINSTEIN GAS
COLLECTIVE EXCITATIONS
ENERGY LEVELS
FLUCTUATIONS
MATHEMATICAL SOLUTIONS
POLYNOMIALS
POTENTIALS
S WAVES
SCATTERING LENGTHS
STABILITY
SUPERFLUIDITY
SYMMETRY
THOMAS-FERMI MODEL
TRAPPING
TRAPS
ATOMIC MODELS
DIMENSIONS
ENERGY-LEVEL TRANSITIONS
EXCITATION
FUNCTIONS
LENGTH
MATHEMATICAL MODELS
PARTIAL WAVES
VARIATIONS