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Modeling quantum fluid dynamics at nonzero temperatures

Lookup NU author(s): Professor Nikolaos Proukakis

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Abstract

The detailed understanding of the intricate dynamics of quantum fluids, in particular in the rapidly growing subfield of quantum turbulence which elucidates the evolution of a vortex tangle in a superfluid, requires an in-depth understanding of the role of finite temperature in such systems. The Landau two-fluidmodel is the most successful hydrodynamical theory of superfluid helium, but by the nature of the scale separations it cannot give an adequate description of the processes involving vortex dynamics and interactions. In our contribution we introduce a framework based on a nonlinear classical-field equation that is mathematically identical to the Landau model and provides a mechanism for severing and coalescence of vortex lines, so that the questions related to the behavior of quantized vortices can be addressed self-consistently. The correct equation of state as well as nonlocality of interactions that leads to the existence of the roton minimum can also be introduced in such description. We review and apply the ideas developed for finite-temperature description of weakly interacting Bose gases as possible extensions and numerical refinements of the proposed method. We apply this method to elucidate the behavior of the vortices during expansion and contraction following the change in applied pressure. We show that at low temperatures, during the contraction of the vortex core as the negative pressure grows back to positive values, the vortex line density grows through a mechanism of vortex multiplication. This mechanism is suppressed at high temperatures.


Publication metadata

Author(s): Berloff NG, Brachet M, Proukakis NP

Publication type: Article

Publication status: Published

Journal: Proceedings of the National Academy of Sciences of the United States of America

Year: 2014

Volume: 111

Issue: Supplement 1

Pages: 4675-4682

Print publication date: 25/03/2014

Online publication date: 24/03/2014

ISSN (print): 0027-8424

Publisher: National Academy of Sciences

URL: http://dx.doi.org/10.1073/pnas.1312549111

DOI: 10.1073/pnas.1312549111


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