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Self-consistent perturbation expansion for Bose-Einstein condensates satisfying Goldstone's theorem and conservation laws
| Title: | Self-consistent perturbation expansion for Bose-Einstein condensates satisfying Goldstone's theorem and conservation laws |
| Authors: | Kita, Takafumi Browse this author →KAKEN DB |
| Issue Date: | 1-Dec-2009 |
| Publisher: | American Physical Society |
| Journal Title: | Physical Review B |
| Volume: | 80 |
| Issue: | 21 |
| Start Page: | 214502 |
| Publisher DOI: | 10.1103/PhysRevB.80.214502 |
| Abstract: | Quantum-field-theoretic descriptions of interacting condensed bosons have suffered from the lack of self-consistent approximation schemes satisfying Goldstone's theorem and dynamical conservation laws simultaneously. We present a procedure to construct such approximations systematically by using either an exact relation for the interaction energy or the Hugenholtz-Pines relation to express the thermodynamic potential in a Luttinger-Ward form. Inspection of the self-consistent perturbation expansion up to the third order with respect to the interaction shows that the two relations yield a unique identical result at each order, reproducing the conserving-gapless mean-field theory [T. Kita, J. Phys. Soc. Jpn. 74, 1891 (2005)] as the lowest-order approximation. The uniqueness implies that the series becomes exact when infinite terms are retained. We also derive useful expressions for the entropy and superfluid density in terms of Green's function and a set of real-time dynamical equations to describe thermalization of the condensate. |
| Rights: | ©2009 The American Physical Society |
| Type: | article |
| URI: | http://hdl.handle.net/2115/42551 |
| Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 北 孝文
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