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Title: Vortex lattices in Bose-Einstein condensates with dipolar interactions beyond the weak-interaction limit

Abstract

We study the ground states of rotating atomic Bose-Einstein condensates with dipolar interactions. We present the results of numerical studies on a periodic geometry which show vortex lattice ground states of various symmetries: triangular and square vortex lattices, stripe crystal, and bubble crystal. We present the phase diagram (for systems with a large number of vortices) as a function of the ratio of dipolar to contact interactions and of the chemical potential. We discuss the experimental requirements for observing transitions between vortex lattice ground states via dipolar interactions. We finally investigate the stability of mean-field supersolid phases of a quasi-two-dimensional nonrotating Bose gas with dipolar interactions.

Authors:
 [1];  [2];  [3]
  1. Theory of Condensed Matter Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, (United Kingdom)
  2. (Germany)
  3. Theory of Condensed Matter Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
Publication Date:
OSTI Identifier:
20982174
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevA.75.023623; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BOSE-EINSTEIN CONDENSATION; BOSE-EINSTEIN GAS; BUBBLES; CRYSTAL LATTICES; GROUND STATES; MEAN-FIELD THEORY; NUMERICAL ANALYSIS; PERIODICITY; PHASE DIAGRAMS; POTENTIALS; STABILITY; SYMMETRY; TWO-DIMENSIONAL CALCULATIONS; VORTICES

Citation Formats

Komineas, S., Max-Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187, Dresden, and Cooper, N. R.. Vortex lattices in Bose-Einstein condensates with dipolar interactions beyond the weak-interaction limit. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.023623.
Komineas, S., Max-Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187, Dresden, & Cooper, N. R.. Vortex lattices in Bose-Einstein condensates with dipolar interactions beyond the weak-interaction limit. United States. doi:10.1103/PHYSREVA.75.023623.
Komineas, S., Max-Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187, Dresden, and Cooper, N. R.. Thu . "Vortex lattices in Bose-Einstein condensates with dipolar interactions beyond the weak-interaction limit". United States. doi:10.1103/PHYSREVA.75.023623.
@article{osti_20982174,
title = {Vortex lattices in Bose-Einstein condensates with dipolar interactions beyond the weak-interaction limit},
author = {Komineas, S. and Max-Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187, Dresden and Cooper, N. R.},
abstractNote = {We study the ground states of rotating atomic Bose-Einstein condensates with dipolar interactions. We present the results of numerical studies on a periodic geometry which show vortex lattice ground states of various symmetries: triangular and square vortex lattices, stripe crystal, and bubble crystal. We present the phase diagram (for systems with a large number of vortices) as a function of the ratio of dipolar to contact interactions and of the chemical potential. We discuss the experimental requirements for observing transitions between vortex lattice ground states via dipolar interactions. We finally investigate the stability of mean-field supersolid phases of a quasi-two-dimensional nonrotating Bose gas with dipolar interactions.},
doi = {10.1103/PHYSREVA.75.023623},
journal = {Physical Review. A},
number = 2,
volume = 75,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • In this Letter, we investigate the effects of dipole-dipole interactions on the vortex lattices in fast rotating Bose-Einstein condensates. For single planar condensate, we show that the triangular lattice structure will be unfavorable when the s-wave interaction is attractive and exceeds a critical value. It will first change to a square lattice, and then become more and more flat with the increase of s-wave attraction, until the collapse of the condensate. For an array of coupled planar condensates, we discuss how the dipole-dipole interactions between neighboring condensates compete with quantum tunneling processes, which affects the relative displacement of two neighboringmore » vortex lattices and leads to the loss of phase coherence between different condensates.« less
  • In calculations to date [D.-W. Wang and E. Demler, e-print arXiv:0812.1838; M. Klawunn and L. Santos, Phys. Rev. A 80, 013611 (2009)] of multilayer stacks of dipolar condensates, created in one-dimensional optical lattices, the condensates have been assumed to be two dimensional. In a real experiment, however, the condensates do not extend to infinity in the oblate direction, but have to be confined by a trap potential, too. By three-dimensional numerical simulations of this realistic experimental situation we find a crucial dependence of the phonon instability boundary on the number of layers. Moreover, near the boundary of the phonon instability,more » a variety of structured ground-state wave functions emerges, which may indicate the onset of a roton instability [S. Ronen, D. C. E. Bortolotti, and J. L. Bohn, Phys. Rev. Lett. 98, 030406 (2007); R. M. Wilson, S. Ronen, J. L. Bohn, and H. Pu, Phys. Rev. Lett. 100, 245302 (2008)]. We also consider the effect of a variable number of atoms per layer on the appearance of the phonon instability.« less
  • Modulational instability and discrete matter wave solitons in dipolar BECs, loaded into a deep optical lattice, are investigated analytically and numerically. The process of modulational instability of nonlinear plane matter waves in a dipolar nonlinear lattice is studied and the regions of instability are established. The existence and stability of bulk discrete solitons are analyzed analytically and confirmed by numerical simulations. In marked contrast with the usual discrete nonlinear Schroedinger behavior (no dipolar interactions), we found a region where the two fundamental modes are simultaneously unstable, allowing enhanced mobility across the lattice for large norm values. To study the existencemore » and properties of surface discrete solitons, an analysis of the dimer configuration is performed. The properties of symmetric and antisymmetric modes including stability diagrams and bifurcations are investigated in closed form. For the case of a bulk medium, properties of fundamental on-site and intersite localized modes are analyzed. On-site and intersite surface localized modes are studied, and we find that they do not exist when nonlocal interactions predominate with respect to local ones.« less
  • The physics of vortex lines in dipolar condensates is studied. Because of the nonlocality of the dipolar interaction, the 3D character of the vortex plays a more important role in dipolar gases than in typical short-range interacting ones. In particular, the dipolar interaction significantly affects the stability of the transverse modes of the vortex line. Remarkably, in the presence of a periodic potential along the vortexline, the spectrum of transverse modes shows a rotonlike minimum, which eventually destabilizes the straight vortex when the BEC as a whole is still stable, opening the possibility for new scenarios for vortex-line configurations inmore » dipolar gases.« less
  • A homogeneous polarized dipolar Bose-Einstein condensate is considered in the presence of weak quenched disorder within mean-field theory at zero temperature. By first solving perturbatively the underlying Gross-Pitaevskii equation and then performing disorder ensemble averages for physical observables, it is shown that the anisotropy of the two-particle interaction is passed on to both the superfluid density and the sound velocity.