Static-response theory and the roton-maxon spectrum of a flattened dipolar Bose-Einstein condensate
Authors: Bisset R. N., Blakie P.B., Stringari S.
Autors Affiliation: Univ Trento, INO CNR BEC Ctr, I-38123 Povo, Italy; Univ Trento, Dipartimento Fis, I-38123 Povo, Italy; Leibniz Univ Hannover, Inst Theoret Phys, D-30167 Hannover, Germany; Univ Otago, Ctr Quantum Sci, Dept Phys, Dunedin 9016, New Zealand;Univ Otago, Dodd Walls Ctr Photon & Quantum Technol, Dunedin 9016, New Zealand
Abstract: Important information for the roton-maxon spectrum of a flattened dipolar Bose-Einstein condensate is extracted by applying a static perturbation exhibiting a periodic in-plane modulation. By solving the Gross-Pitaevskii equation in the presence of the weak perturbation, we evaluate the linear density response of the system and use it, together with sum rules, to provide a Feynman-like upper-bound prediction for the excitation spectrum, finding excellent agreement with the predictions of full Bogoliubov calculations. By suddenly removing the static perturbation, while still maintaining the trap, we find that the density modulations-as well as the weights of the perturbation-induced side peaks of the momentum distribution-undergo an oscillatory behavior with double the characteristic frequency of the excitation spectrum. The measurement of the oscillation periods could provide an easy determination of dispersion relations.
Journal/Review: PHYSICAL REVIEW A
Volume: 100 (1) Pages from: 013620-1 to: 013620-6