2005/03/31 by Flavio S. Nogueira, H. Kleinert, Hagen Kleinert
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Physics of Superconductivity and Magnetism #Quantum, superfluid, helium dynamics #cond-mat.other
paper · pdf · doi:10.1103/physrevb.73.104515
published as Phys. Rev. B 73, 104515 (2006) · 21 pages; 2 figures; v4: version accepted for publication in PRB; in this version Section IV is considerably extended
arxiv created 2006/02/28 · openalex publication_date 2006/03/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We show that rotonlike excitations are thermally induced in a two-dimensional dilute Bose gas as a consequence of the strong phase fluctuations in two dimensions. At low momentum, the rotonlike excitations lead for small enough temperatures to an anomalous phonon spectrum with a temperature-dependent exponent reminiscent of the Kosterlitz-Thouless transition. Despite the anomalous form of the energy spectrum, it is shown that the corresponding effective theory of vortices describes the usual Kosterlitz-Thouless transition. The possible existence of an anomalous normal state in a small temperature interval is also discussed.