Tapio P. Simula

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We have performed numerical simulations of giant vortex structures in rapidly rotating Bose-Einstein condensates within the Gross-Pitaevskii formalism. We reproduce the qualitative features, such as oscillation of the giant vortex core area, formation of toroidal density hole, and the precession of giant vortices, observed in the recent experiment [Phys.(More)
Here we show, by performing ab initio classical field simulations that two distinct superfluid phases, separated by thermal vortex-antivortex pair creation, exist in experimentally producible quasi-2D Bose gas. These results resolve the debate on the nature of the low temperature phase(s) of a trapped interacting 2D Bose gas.
R. N. Bisset, M. J. Davis, T. P. Simula, and P. B. Blakie Department of Physics, Jack Dodd Centre for Quantum Technology, University of Otago, Dunedin 9016 New Zealand ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia Department of Physics, Okayama University,(More)
An aberration corrected electron microscope is used to create electron diffraction catastrophes, containing arrays of intensity zeros threading vortex cores. Vortices are ascribed to these arrays using catastrophe theory, scalar diffraction integrals, and experimentally retrieved phase maps. From measured wave function phases, obtained using focal-series(More)
T. P. Simula, M. J. Davis, and P. B. Blakie Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark Laboratory of Physics, Helsinki University of Technology, P.O.Box 1100, FI-02015 TKK, Finland ARC Centre of Excellence for Quantum-Atom Optics, School of Physical(More)
Multiply quantized vortices in trapped Bose-Einstein condensates are studied using the Bogoliubov theory. Suitable combinations of a localized pinning potential and an external rotation of the system are found to energetically stabilize, both locally and globally, vortices with multiple circulation quanta. We present a phase diagram for stable multiply(More)
Rights: © 2000 American Physical Society (APS). This is the accepted version of the following article: Hellén, E. K. O. & Simula, T. P. & Alava, Mikko J. 2000. Dynamic scaling in one-dimensional cluster-cluster aggregation. Physical Review E. Volume 62, Issue 4. 4752-4756. ISSN 1539-3755 (printed). DOI: 10.1103/physreve.62.4752, which has been published in(More)
We compute the structure of a quantized vortex line in a harmonically trapped dilute atomic Bose-Einstein condensate using the Popov version of the Hartree-Fock-Bogoliubov mean-field theory. The vortex is shown to be (meta)stable in a nonrotating trap even in the zero-temperature limit, thus confirming that weak particle interactions induce for the(More)
Repulsive laser potential pulses applied to vortex lattices of rapidly rotating Bose-Einstein condensates create propagating density waves which we have observed experimentally and modeled computationally to high accuracy. We have observed a rich variety of dynamical phenomena ranging from interference effects and shock-wave formation to anisotropic sound(More)