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Thermally induced rotons in two-dimensional dilute Bose gases

Flavio S. Nogueira·Hagen Kleinert
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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.

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Flavio S. Nogueira, Hagen Kleinert. 2006-02-28. Thermally induced rotons in two-dimensional dilute Bose gases. https://doi.org/10.1103/physrevb.73.104515

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