Elementary excitations and universal interaction in Bose-Einstein condensates at large scattering lengths

Journal Article · Sat Oct 15 00:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.84.041602· OSTI ID:22080301

Sarjonen, R; Saarela, M; Mazzanti, F ^[1]

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1. Department of Physics, P.O. Box 3000, FIN-90014, University of Oulu (Finland)

We present a theoretical analysis of excitation modes in Bose-Einstein condensates of ultracold alkali-metal gases for large scattering lengths, showing clear deviations from the Bogoliubov prediction as seen by Papp et al.[Phys. Rev. Lett. 101, 135301 (2008)]. We construct the atom-atom interaction by deriving the T matrix of such systems from two coupled (open and closed) channels assuming that the Feshbach resonance dominates the latter. We calculate molecular bound-state energies as a function of the magnetic field and compare with available experiments. The s-wave phase shifts determine the local effective interaction with long-ranged repulsion and short-ranged attraction. We show that it becomes a universal function at large scattering lengths. Finally, we use this interaction to characterize the ground-state and elementary excitations of {sup 85}Rb, {sup 87}Rb, and {sup 23}Na gases. Good agreement with line shift experiments in {sup 85}Rb is achieved. We find that, at large scattering lengths, Bragg scattering experiments could directly measure the momentum dependence of the effective two-body potential.

• OSTI ID: 22080301
• Journal Information: Physical Review. A, Vol. 84, Issue 4; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METALS
ATOMS
BOSE-EINSTEIN CONDENSATION
BOUND STATE
EXCITATION
GASES
GROUND STATES
INTERACTIONS
MAGNETIC FIELDS
PHASE SHIFT
RUBIDIUM 85
RUBIDIUM 87
S MATRIX
S WAVES
SCATTERING
SCATTERING LENGTHS
SODIUM 23
TWO-BODY PROBLEM