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Title: Comparing Contact and Dipolar Interactions in a Bose-Einstein Condensate

Abstract

We have measured the relative strength {epsilon}{sub dd} of the magnetic dipole-dipole interaction compared with the contact interaction in a dipolar chromium Bose-Einstein condensate. We analyze the asymptotic velocities of expansion of the condensate with different orientations of the atomic magnetic moments. By comparing the experimental results with numerical solutions of the hydrodynamic equations for dipolar condensates, we obtain {epsilon}{sub dd}=0.159{+-}0.034. We use this result to determine the s-wave scattering length a=(5.08{+-}1.06x10{sup -9}) m=(96{+-}20) a{sub 0} of {sup 52}Cr. This is fully consistent with our previous measurements on the basis of Feshbach resonances and therefore confirms the validity of the theoretical approach used to describe the dipolar Bose-Einstein condensate.

Authors:
; ; ; ; ;  [1]
  1. 5. Physikalisches Institut, Universitaet Stuttgart, 70550 Stuttgart (Germany)
Publication Date:
OSTI Identifier:
20861510
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 97; Journal Issue: 25; Other Information: DOI: 10.1103/PhysRevLett.97.250402; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOSE-EINSTEIN CONDENSATION; CHROMIUM; CHROMIUM 52; CONDENSATES; EQUATIONS; MAGNETIC DIPOLES; MAGNETIC MOMENTS; NUMERICAL SOLUTION; RESONANCE; S WAVES; SCATTERING LENGTHS; VELOCITY

Citation Formats

Griesmaier, Axel, Stuhler, Juergen, Koch, Tobias, Fattori, Marco, Pfau, Tilman, and Giovanazzi, Stefano. Comparing Contact and Dipolar Interactions in a Bose-Einstein Condensate. United States: N. p., 2006. Web. doi:10.1103/PHYSREVLETT.97.250402.
Griesmaier, Axel, Stuhler, Juergen, Koch, Tobias, Fattori, Marco, Pfau, Tilman, & Giovanazzi, Stefano. Comparing Contact and Dipolar Interactions in a Bose-Einstein Condensate. United States. doi:10.1103/PHYSREVLETT.97.250402.
Griesmaier, Axel, Stuhler, Juergen, Koch, Tobias, Fattori, Marco, Pfau, Tilman, and Giovanazzi, Stefano. Fri . "Comparing Contact and Dipolar Interactions in a Bose-Einstein Condensate". United States. doi:10.1103/PHYSREVLETT.97.250402.
@article{osti_20861510,
title = {Comparing Contact and Dipolar Interactions in a Bose-Einstein Condensate},
author = {Griesmaier, Axel and Stuhler, Juergen and Koch, Tobias and Fattori, Marco and Pfau, Tilman and Giovanazzi, Stefano},
abstractNote = {We have measured the relative strength {epsilon}{sub dd} of the magnetic dipole-dipole interaction compared with the contact interaction in a dipolar chromium Bose-Einstein condensate. We analyze the asymptotic velocities of expansion of the condensate with different orientations of the atomic magnetic moments. By comparing the experimental results with numerical solutions of the hydrodynamic equations for dipolar condensates, we obtain {epsilon}{sub dd}=0.159{+-}0.034. We use this result to determine the s-wave scattering length a=(5.08{+-}1.06x10{sup -9}) m=(96{+-}20) a{sub 0} of {sup 52}Cr. This is fully consistent with our previous measurements on the basis of Feshbach resonances and therefore confirms the validity of the theoretical approach used to describe the dipolar Bose-Einstein condensate.},
doi = {10.1103/PHYSREVLETT.97.250402},
journal = {Physical Review Letters},
number = 25,
volume = 97,
place = {United States},
year = {Fri Dec 22 00:00:00 EST 2006},
month = {Fri Dec 22 00:00:00 EST 2006}
}
  • The dynamics of Bose-Einstein condensates in optical lattices with the long-range dipole-dipole interactions, the short-range on-site interactions, and hopping terms is reduced to the generalized discrete nonlinear Schroedinger equation. We present the different types of solitary excitations which appear in different parameter regions. We anticipate that these excitations will be observable and discuss how the model parameters can be tuned in experiments.
  • Our recent measurements on the expansion of a chromium dipolar condensate after release from an optical trapping potential are in good agreement with an exact solution of the hydrodynamic equations for dipolar Bose gases. We report here the theoretical method used to interpret the measurement data as well as more details of the experiment and its analysis. The theory reported here is a tool for the investigation of different dynamical situations in time-dependent harmonic traps.
  • We analyze the hydrodynamic solutions for a dilute Bose-Einstein condensate with long-range dipolar interactions in a rotating, elliptical harmonic trap. The static solutions and their regimes of dynamical instability vary nontrivially with the strength of the dipolar interactions. We comprehensively map out this behavior, and, in particular, examine the experimental routes toward unstable dynamics, which, in analogy to conventional condensates, may lead to vortex lattice formation.
  • We present a variational method to study the ground state of the newly realized {sup 52}Cr dipolar Bose-Einstein condensate. Besides the usual contact potential term in the mean-field equation, there is an additional long-range and anisotropic dipole-dipole interaction potential. We develop an efficient Newton-Raphson's scheme to solve the condensate state. The solution shows a double-peak feature in the loosely confined dimension. Compared to the existing single-peak calculations, the double-peak solution has lower energy and reflects the distinct property of the dipole-dipole interaction. Our method is easy and efficient to use for future investigations of the dipolar systems.
  • Helical spin textures in a {sup 87}Rb F=1 spinor Bose-Einstein condensate are found to decay spontaneously toward a spatially modulated structure of spin domains. The formation of this modulated phase is ascribed to magnetic dipolar interactions that energetically favor the short-wavelength domains over the long-wavelength spin helix. The reduction of dipolar interactions by a sequence of rf pulses results in a suppression of the modulated phase, thereby confirming the role of dipolar interactions in this process. This study demonstrates the significance of magnetic dipole interactions in degenerate {sup 87}Rb F=1 spinor gases.