Spin-1 atomic condensates in magnetic fields

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1853/7495

Title: Spin-1 atomic condensates in magnetic fields
Author: Zhang, Wenxian
Abstract: 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.
Type: Dissertation
URI: http://hdl.handle.net/1853/7495
Date: 2005-09-22
Publisher: Georgia Institute of Technology
Subject: BEC
Spinor
Zeeman effects
Zeeman effect
Bose-Einstein gas
Magnetic fields
Spinor analysis
Department: Physics
Advisor: Committee Chair: Li You; Committee Member: Chandra Raman; Committee Member: Mei-Yin Chou; Committee Member: Michael S. Chapman; Committee Member: Z. John Zhang
Degree: Ph.D.

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