Thermally induced rotons in two-dimensional dilute Bose gases

Abstract

We show that roton-like 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 roton-like 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.

arXiv comment21 pages; 2 figures; v4: version accepted for publication in PRB; in this version Section IV is considerably extended

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Cited by in corpus (7)

• Weakly Interacting, Dilute Bose Gases in 2D
• Softening of Roton and Phonon Modes in a Bose-Einstein Condensate with Spin-Orbit Coupling
• Roton-Maxon Excitation Spectrum of Bose Condensates in a Shaken Optical Lattice
• Anomalous scaling at non-thermal fixed points of the sine-Gordon model
• Phase diagram for interacting Bose gases
• Large-$N$ properties of a non-ideal Bose gas
• Negative refraction and rotons in the relativistic Bose gas