Collective excitations of the hybrid atomic-molecular Bose-Einstein condensates

Journal Article · Tue Jun 15 00:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.81.063631· OSTI ID:21439527

Gupta, Moumita; Dastidar, Krishna Rai ^[1]

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1. Department of Spectroscopy, Indian Association for the Cultivation of Science, Kolkata 700032 (India)

We investigate the low-energy excitations of the spherically and axially trapped atomic Bose-Einstein condensate coupled to a molecular Bose gas by coherent Raman transitions. We apply the sum-rule approach of many-body response theory to derive the low-lying collective excitation frequencies of the hybrid atom-molecular system. The atomic and molecular ground-state densities obtained in Gross-Pitaevskii and modified Gross-Pitaevskii (including the higher order Lee-Huang-Yang term in interatomic interaction) approaches are used to find out the individual energy components and hence the excitation frequencies. We obtain different excitation energies for different angular momenta and study their characteristic dependence on the effective Raman detuning, the scattering length for atom-atom interaction, and the intensities of the coupling lasers. We show that the inclusion of the higher-order nonlinear interatomic interaction in modified Gross-Pitaevskii approach introduces significant corrections to the ground-state properties and the excitation frequencies both for axially and spherically trapped coupled {sup 87}Rb condensate system with the increase in the s-wave scattering length (for peak gas-parameter {>=}10{sup -3}). It has been shown that the excitation frequencies decrease with the increase in the effective Raman detuning as well as the s-wave scattering length, whereas excitation frequencies increase with the increase in the atom-molecular coupling strength. The frequencies in modified Gross-Pitaevskii approximation exhibit an upward trend after a certain value of scattering length and also largely deviate from the Gross-Pitaevskii results with the increase in s-wave scattering length. The strong dependence of excitation frequencies on the laser intensities used for Raman transitions manifests the role of atom-molecular coupling strength on the control of collective excitations. The collective excitation frequencies for the hybrid atom-molecular BEC differ significantly from the excitation frequencies of a pure atomic BEC system when the atom-to-molecule conversion efficiency increases due to the decrease in the effective Raman detuning and increase in the atom-molecule coupling strength.

• OSTI ID: 21439527
• Journal Information: Physical Review. A, Vol. 81, Issue 6; Other Information: DOI: 10.1103/PhysRevA.81.063631; (c) 2010 The American Physical Society; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ANGULAR MOMENTUM
APPROXIMATIONS
ATOMS
BOSE-EINSTEIN CONDENSATION
BOSE-EINSTEIN GAS
COLLECTIVE EXCITATIONS
COUPLING
INTERATOMIC FORCES
MANY-BODY PROBLEM
MOLECULES
NONLINEAR PROBLEMS
RUBIDIUM 87
S WAVES
SCATTERING LENGTHS
SUM RULES
TRAPPING
WAVE EQUATIONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCULATION METHODS
DIFFERENTIAL EQUATIONS
DIMENSIONS
ENERGY-LEVEL TRANSITIONS
EQUATIONS
EXCITATION
INTERMEDIATE MASS NUCLEI
ISOTOPES
LENGTH
NUCLEI
ODD-EVEN NUCLEI
PARTIAL DIFFERENTIAL EQUATIONS
PARTIAL WAVES
RADIOISOTOPES
RUBIDIUM ISOTOPES
YEARS LIVING RADIOISOTOPES