The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Stability and Dynamics of Quantized Vortices in Gaseous Bose-Einstein Condensates

Jukka Huhtamäki

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Information and Natural Sciences for public examination and debate in Auditorium D at Helsinki University of Technology (Espoo, Finland) on the 7th of March, 2008, at 13 o'clock.

Overview in PDF format (ISBN 978-951-22-9256-1)   [1844 KB]
Dissertation is also available in print (ISBN 978-951-22-9255-4)

Abstract

Bose-Einstein condensation is a quantum statistical phase transition which was theoretically predicted almost a hundred years ago. After years of seminal research, physicists realized the first almost ideal Bose-Einstein condensates in ultracold dilute atomic gases in 1995. Since then, the theoretical and experimental methods concerning such systems have been developing rapidly, and many fascinating phenomena have been found in these novel quantum systems.

Bose-Einstein condensation occurs in a system consisting of massive bosons when a single quantum state becomes macroscopically occupied as the temperature is lowered below the transition temperature. In general, condensates consisting of repulsively interacting bosons exhibit superfluidity: Particle currents can flow in the system without dissipation and viscosity. Moreover, the velocity fields of condensates have to be irrotational, which severely restricts the rotational characteristics of these systems. Apart from the center of mass motion, the system may carry angular momentum in the form of elementary excitations or so-called quantized vortices.

This Thesis is a theoretical study of subjects related to stability and dynamics of quantized vortices in dilute atomic Bose-Einstein condensates. The precession and instability of off-centered vortices in trapped condensates is investigated both in the zero-temperature limit and at finite temperatures. Dynamical stability of multiply quantized vortices and vortex clusters is studied in axisymmetric trap geometries. Splitting of energetically and dynamically unstable multiply quantized vortices into singly quantized vortices is also studied. Finally, as a separate subject, tunneling of a condensate through a potential barrier is investigated. Majority of this work relies on numerical methods for solving the Gross-Pitaevskii and Bogoliubov equations, which are of central importance in the study of dilute atomic Bose-Einstein condensates.

This thesis consists of an overview and of the following 7 publications:

  1. Tomoya Isoshima, Jukka Huhtamäki, and Martti M. Salomaa, Instabilities of off-centered vortices in a Bose-Einstein condensate, Physical Review A 68, 033611 (2003). © 2003 American Physical Society. By permission.
  2. Tomoya Isoshima, Jukka Huhtamäki, and Martti M. Salomaa, Precessional motion of a vortex in a finite-temperature Bose-Einstein condensate, Physical Review A 69, 063601 (2004). © 2004 American Physical Society. By permission.
  3. J. A. M. Huhtamäki, M. Möttönen, and S. M. M. Virtanen, Dynamically stable multiply quantized vortices in dilute Bose-Einstein condensates, Physical Review A 74, 063619 (2006). © 2006 American Physical Society. By permission.
  4. V. Pietilä, M. Möttönen, T. Isoshima, J. A. M. Huhtamäki, and S. M. M. Virtanen, Stability and dynamics of vortex clusters in nonrotated Bose-Einstein condensates, Physical Review A 74, 023603 (2006). © 2006 American Physical Society. By permission.
  5. J. A. M. Huhtamäki, M. Möttönen, T. Isoshima, V. Pietilä, and S. M. M. Virtanen, Splitting times of doubly quantized vortices in dilute Bose-Einstein condensates, Physical Review Letters 97, 110406 (2006). © 2006 American Physical Society. By permission.
  6. T. Isoshima, M. Okano, H. Yasuda, K. Kasa, J. A. M. Huhtamäki, M. Kumakura, and Y. Takahashi, Spontaneous splitting of a quadruply charged vortex, Physical Review Letters 99, 200403 (2007). © 2007 American Physical Society. By permission.
  7. J. A. M. Huhtamäki, M. Möttönen, J. Ankerhold, and S. M. M. Virtanen, Effects of interactions and noise on tunneling of Bose-Einstein condensates through a potential barrier, Physical Review A 76, 033605 (2007). © 2007 American Physical Society. By permission.

Keywords: Bose-Einstein condensation, superfluidity, vortex

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© 2008 Helsinki University of Technology

Last update 2011-05-26