Renormalization of the superfluid density in the two-dimensional BCS-BEC crossover Journal Article

Author(s): Bighin, Giacomo; Salasnich, Luca
Article Title: Renormalization of the superfluid density in the two-dimensional BCS-BEC crossover
Affiliation IST Austria
Abstract: We analyze the theoretical derivation of the beyond-mean-field equation of state for two-dimensional gas of dilute, ultracold alkali-metal atoms in the Bardeen–Cooper–Schrieffer (BCS) to Bose–Einstein condensate (BEC) crossover. We show that at zero temperature our theory — considering Gaussian fluctuations on top of the mean-field equation of state — is in very good agreement with experimental data. Subsequently, we investigate the superfluid density at finite temperature and its renormalization due to the proliferation of vortex–antivortex pairs. By doing so, we determine the Berezinskii–Kosterlitz–Thouless (BKT) critical temperature — at which the renormalized superfluid density jumps to zero — as a function of the inter-atomic potential strength. We find that the Nelson–Kosterlitz criterion overestimates the BKT temperature with respect to the renormalization group equations, this effect being particularly relevant in the intermediate regime of the crossover.
Keywords: Bardeen–Cooper–Schrieffer condensate crossover; Berezinskii–Kosterlitz–Thouless critical temperature; Bose–Einstein condensate crossover; superfluid density
Journal Title: International Journal of Modern Physics B
ISSN: 1793-6578
Publisher: World Scientific Publishing  
Date Published: 2018-01-01
Start Page: Epub ahead of print
DOI: 10.1142/S0217979218400222
Open access: yes (repository)
IST Austria Authors
  1. Giacomo Bighin
    5 Bighin
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