Quasi-one dimensional degenerate Bose gas

Tarun Kanti Ghosh

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arXiv · cond-mat/0402079

Quasi-one dimensional degenerate Bose gas

Tarun Kanti Ghosh

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Abstract

Motivated by the MIT experiment [Gorlitz {\em et al.}, Phys. Rev. Lett. {\bf 87}, 130402 (2001)], we analytically study the effect of density and phase fluctuations on various observables in a quasi one-dimensional degenerate Bose gases. Quantizing the Gross-Pitaevskii Hamiltonian and diagonalize it in terms of the normal modes associated with the density and phase fluctuations of a quasi-one dimensional Bose gas. We calculate dynamic structure factor $S(q,ω)$ from low-energy condensate density fluctuations and find that there are multiple peaks in $S(q,ω)$ for a given momentum $q$ due to the discrete energy spectrum. These multiple peaks can be resolved by a two-photon Bragg pulse with a long duration which transfer the momentum to the system. We calculate the momentum transferred $ P_z(t)$ by using the phase-density representation of the Bose order parameter. We also calculate the single-particle density matrix, phase coherence length, and momentum distribution by taking care of the phase fluctuations upto fourth-order term as well as the density fluctuations. Our studies on coherence properties shows that 1D Bose gases of MIT experiment do not form a true condensate, but it can be obtained by a moderate changes of the current experimental parameters.

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Tarun Kanti Ghosh. 2004-03-05. Quasi-one dimensional degenerate Bose gas. https://arxiv.org/abs/cond-mat/0402079

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