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

Year: 2018

Authors: Birghin G., Salasnich L.

Autors Affiliation: Bighin, G.] IST Austria, Campus 1, A-3400 Klosterneuburg, Austria.
[Salasnich, L.] Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Via Marzolo 8, I-35131 Padua, Italy and Univ Padua, CNISM, Via Marzolo 8, I-35131 Padua, Italy and CNR INO, Via Nello Carrara, I-50019 Sesto Fiorentino, Italy.

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.

Journal/Review: INTERNATIONAL JOURNAL OF MODERN PHYSICS B

Volume: 32 (17)      Pages from: 1840022-1  to: 1840022-9

KeyWords: Bose-Einstein condensate crossover; Bardeen-Cooper-Schrieffer condensate cro; Berezinskii-Kosterlitz-Thouless critical; superfluid density; strong-coupling superconductivity
DOI: 10.1142/S0217979218400222

Citations: 5
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