Effects of the dipole-dipole interaction on the properties of ultracold rotating dipolar gases
Final Report Abstract
The research on dipolar gases currently constitutes one of most active research topics in the physics of cold atoms. This interest is motivated by recent experiments on atoms with large magnetic moments (in particular the recently achieve Chromium condensate), on polar molecules, and on Rydberg atoms. The main goal of this project was originally the study of the vortex formation in dipolar gases, as well as the dipolar effects in vortex lattices. However, the works performed by competing works in the mean time have led us to reformulate our original strategy. The analytical and numerical techniques which were originally developed for the analysis of vortices in two-dimensional dipolar condensates have been successfully applied to the analysis of the effects of nonlocal nonlinearity (a major topic in nonlinear physics) in dipolar gases. In particular we have shown that stable two dimensional solitons are possible in dipolar gases, contrary to usual condensates. In addition the solitons have been shown to scatter inelastic in a nontrivial way. Additionally, these techniques have been employed in the study of the expansion and lowest-lying excitations of non axi-symmetric dipolar condensates. This analysis has been successfully applied to explain recent milestone experiments at Stuttgart University, whose results coincide excellently with our predictions. Additionally, we have localized during this initial year two new interesting problems, which are expected to be of fundamental interest for the future analysis of rotating (and also nonrotating) dipolar gases. On one side we have studied the scattering properties of dipolar gases in elongated atomic waveguides. We have shown that the expected confinement-induced resonance is significantly affected by the dipole-dipole interaction, which may change the sign of the asymptotic 1D scattering length. This may have very relevant consequences in the physics of dipolar condensates in waveguides, as well as strongly-correlated dipolar gases in 1D. On the other side, we have studied the dipole-induced transfer of spin into center-of-mass rotation in spin-3 Chromium condensates, and effect which resembles the well-known Einstein de Haas effect.
Publications
- "Observation of dipole-dipole interaction in a degenerate quantum gas", J. Stuhler, A. Griesmaier, T. Koch, M. Fattori, T. Pfau, S. Giovanazzi, P. Pedri, and L. Santos, Phys. Rev. Lett. 95, 150406 (2005); condmat/ 0508228.
- "Spin-3 Chromium Bose-Einstein condensates", L. Santos and T. Pfau, cond-mat/0510634; Phys. Rev. Lett. 96, 190404 (2006).
- "Two-dimensional bright solitons in dipolar Bose-Einstein condensates", P. Pedri and L. Santos, Phys. Rev. Lett. 95, 200404 (2005); condmat/ 0503019.
