In this thesis we investigate the static, dynamic, and thermodynamic properties
of atomic spin-1 Bose gases in external magnetic fields. At low magnetic fields
the properties of single-component, or scalar condensates, are essentially
unaffected but can become significantly altered for spinor Bose condensates as
shown by our studies.
We first study the Bose-Einstein condensation of trapped spin-1 Bose gases by
employing the Hartree-Fock approximation and the two-fluid model within a mean
field approximation. Our detailed investigation reveals that the
ferromagnetically interacting spin-1 condensates exhibit triple condensations
while the antiferromagnetically interacting ones show double condensations.
The ground state structure of homogeneous and trapped spin-1 Bose condensates
with ferromagnetic and antiferromagnetic interactions at zero temperature in
magnetic fields are then investigated systematically. We further illuminate the
important effect of quadratic Zeeman shift which causes a preferred occupation
of the $|m_F=0
angle$ state through spin exchange collisions, $2|m_F=0
angle
leftrightarrow |m_F=1
angle + |m_F=-1
angle$.
We also present detailed studies of the off-equilibrium coherent dynamics of
spin-1 Bose condensates in magnetic fields within the single spatial mode
approximation. Dynamical instabilities of the off-equilibrium oscillations are
shown to be responsible for the formation of multiple domains as recently
observed in several $^{87}$Rb experiments.
Finally, we discuss briefly excited condensate states, or soliton-like states,
in cigar-shaped spin-1 Bose condensates with an effective quasi-1D description,
using the developed nonpolynomial Schr"odinger equation.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/7495 |
| Date | 22 September 2005 |
| Creators | Zhang, Wenxian |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
| Format | 1470944 bytes, application/pdf |
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