|
|
Quick Links to: Introduction, Movies , Paper
 |
|
|
|
Thermal Vortex-Pair Creation in 2D Bose-Einstein Condensates
T. P. Simula and P. B. Blakie
Department of Physics, University of Otago, Dunedin, New Zealand.
At ultra-low temperatures dilute 3D Bose gas undergoes Bose-Einstein condensation
(BEC) and becomes superfluid. In homogeneous 2D systems, BEC does not occur in
the thermodynamic limit and super
fluidity is instead achieved through the Berezinskii-
Kosterlitz-Thouless (BKT) transition. In the presence of harmonic trapping, however,
both BEC and BKT phases have been predicted to co-exist [1,2]. Recently, experimental
observation of phase defects in quasi-2D condensates have been reported [3].
We have performed classical field simulations suggesting that the experimentally observed
phase defects can be explained in terms of thermally activated vortex-antivortex pairs [2].
The figure below shows computed spatial densities (a,b,c) and the corresponding phase
profiles (d,e,f) of the gas at the respective temperatures, T = (0.2, 0.7 and 0.9)T0, below
the ideal-gas BEC temperature, T0. The low temperature phase coherent BEC (a,d), and
the phase
fluctuating BKT (c,f) phases are separated by a vortex-pair creation transition.
As temperature is further increased the super
fluidity is destroyed at the BKT-normal
transition.
| |
| |
Click Image to enlarge
|
|
|
[1] T. P. Simula, M. D. Lee and D. A. W. Hutchinson, Phil. Mag. Lett 85, 395 (2005). link.
[2] T. P. Simula and P. B. Blakie, Phys. Rev. Lett. 96, 020404 (2006). link.
[3] S. Stock, Z. Hadzibabic, B. Battelier, M. Cheneau and J. Dalibard, Phys. Rev. Lett. 95, 190403 (2005). link.
| |
|
|
Movies
Currently we have two movies of our simulations available in mpeg4 and AVI formats.
| |
|
|
|
|
Movie 1:
Dynamics of vortex pairs in the BKT phase at constant temperature for
the case in Fig.3 of [Phys. Rev. Lett. 96, 020404 (2006)] .
[mpeg4 format, 3.7MB]
[avi format, 6.7MB]
| |
|
Movie 2:
Propagation of the BEC-BKT transition as a function of temperature for
N=1e4. The diameter of the red circle is one Thomas-Fermi radius.
[mpeg4 format, 3.7MB]
[avi format, 6.7MB]
General Comment:
The system parameters are those used in [Phys. Rev. Lett. 96, 020404 (2006)] . The plus and minus
signs denote the locations of vortices and antivortices, respectively.
| |
|
|
|
| |
Paper
This research, Thermal activation of vortex-antivortex pairs in quasi-2D Bose-Einstein condensates,
T.P. Simula and P. Blair Blakie, is published at [Phys. Rev. Lett. 96, 020404 (2006)]. A preprint is also available: Cond-Mat Archive.
| |
|
