International Journal of Physics | Vol. 1, No. 8, August 2010 | pp. 57–64
Research Article
Title: Collective Excitations and Superfluid Density of Dipolar Bose-Einstein Condensates
Names of Authors: T. U. Vogel¹, U. V. Weber², V. W. Zeller¹
Authors’ Affiliations: ¹Institute for Theoretical Physics, University of Innsbruck, Innsbruck, Austria; ²Max Planck Institute of Quantum Optics, Garching, Germany
Abstract: We analyze the collective modes of an elongated Bose-Einstein condensate composed of chromium-52 atoms possessing strong magnetic dipole-dipole interactions. Using the extended Gross-Pitaevskii equation incorporating dipole orientation angles relative to the trap symmetry axis, we compute the dipole and quadrupole oscillation frequencies omega_z and omega_perp. Anisotropic dipole forces shift the resonant frequencies by up to 18% compared to standard contact-interaction gases. The normal-to-superfluid transition fraction evaluated via two-fluid hydrodynamic equations demonstrates suppression of critical velocity thresholds along the polarization axis. Damping rates measured through anisotropic expansion profiles show resonance peaks near aspect ratio thresholds epsilon_ar = 2.4. Our theoretical model accounts for dipolar relaxation losses and confirms stability regimes governed by the relative dipole-to-s-wave scattering length ratio epsilon_dd = mu_0 * d² * m / (12 * pi * hbar² * a_s).
Keywords: Bose-Einstein condensation, Dipolar gases, Collective excitations, Gross-Pitaevskii equation, Superfluidity
Manuscript Timeline: Received 05 May 2010, Revised 14 June 2010, Accepted 28 June 2010, Published 02 August 2010
Citation: Vogel, T. U., Weber, U. V., & Zeller, V. W. (2010). Collective Excitations and Superfluid Density of Dipolar Bose-Einstein Condensates. International Journal of Physics, 1(8), 57–64. DOI: 10.46882/2010/IJP/000008
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