Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/81632

Download PDF (Accepted manuscript) (Adobe Acrobat PDF, -1 bytes)

Title

Collective oscillations of a confined Bose gas at finite temperature in the random-phase approximation

Author(s)

Liu, Xia-Ji;  Hu, Hui;  Minguzzi, A.;  Tosi, M. P.

Abstract

We present a theory for the linear dynamics of a weakly interacting Bose gas confined inside a harmonic trap at finite temperature. The theory treats the motions of the condensate and of the noncondensate on an equal footing within a generalized random-phase approximation, which (i) extends the second-order Beliaev-Popov approach by allowing for the dynamical coupling between fluctuations in the thermal cloud, and (ii) reduces to an earlier random-phase scheme when the anomalous density fluctuations are omitted. Numerical calculations of the low-lying spectra in the case of isotropic confinement show that the present theory obeys with high accuracy the generalized Kohn theorem for the dipolar excitations and demonstrate that combined normal and anomalous density fluctuations play an important role in the monopolar excitations of the condensate. Mean-field theory is instead found to yield accurate results for the quadrupolar modes of the condensate. Although the restriction to spherical confinement prevents quantitative comparisons with measured spectra, it appears that the non-mean-field effects that we examine may be relevant to explain the features exhibited by the breathing mode as a function of temperature in the experiments carried out at JILA on a gas of ^87Rb atoms.

Publication type

Journal article

Source

Physical Review A: Atomic, Molecular, and Optical Physics, Vol. 69, no. 4 (Apr 2004), article no. 043605

Publication year

2004

FOR Code(s)

0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics;  0204 Condensed Matter Physics;  0205 Optical Physics

Keyword(s)

Approximation theory;  Bose gases;  Frequencies;  Gas condensates;  Gas dynamics;  Hamiltonians;  Mathematical models;  Monopolar excitations;  Oscillations;  Quantum theory;  Random-phase-approximation;  RPA;  Rubidium;  Thermal cloud;  Thermodynamics

Publisher

American Physical Society

ISSN

1050-2947

Publisher URL

http://dx.doi.org/10.1103/PhysRevA.69.043605

Copyright

Copyright © 2004 The American Physical Society. The accepted manuscript of the paper is reproduced here for noncommerical purposes only in accordance with the copyright policy of the publisher.

Full text

Peer reviewed