Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Reliability of the Ginzburg–Landau Theory in the BCS-BEC Crossover by Including Gaussian Fluctuations for 3D Attractive Fermions

Version 1 : Received: 1 December 2021 / Approved: 3 December 2021 / Online: 3 December 2021 (13:55:24 CET)

How to cite: Pascucci, F.; Perali, A.; Salasnich, L. Reliability of the Ginzburg–Landau Theory in the BCS-BEC Crossover by Including Gaussian Fluctuations for 3D Attractive Fermions. Preprints 2021, 2021120055 (doi: 10.20944/preprints202112.0055.v1). Pascucci, F.; Perali, A.; Salasnich, L. Reliability of the Ginzburg–Landau Theory in the BCS-BEC Crossover by Including Gaussian Fluctuations for 3D Attractive Fermions. Preprints 2021, 2021120055 (doi: 10.20944/preprints202112.0055.v1).

Abstract

We calculate the parameters of the Ginzburg–Landau (GL) equation of a three-dimensional attractive Fermi gas around the superfluid critical temperature. We compare different levels of approximation throughout the Bardeen–Cooper–Schrieffer (BCS) to the Bose–Einstein Condensate (BEC) regime. We show that the inclusion of Gaussian fluctuations strongly modifies the values of the Ginzburg–Landau parameters approaching the BEC regime of the crossover. We investigate the reliability of the Ginzburg–Landau theory, with fluctuations, studying the behavior of the coherence length and of the critical rotational frequencies throughout the BCS-BEC crossover. The effect of the Gaussian fluctuations gives qualitative correct trends of the considered physical quantities from the BCS regime up to the unitary limit of the BCS-BEC crossover. Approaching the BEC regime, the Ginzburg–Landau equation with the inclusion of Gaussian fluctuations turns out to be unreliable.

Keywords

Ginzburg–Landau theory; BCS-BEC crossover; pair fluctuations

Subject

PHYSICAL SCIENCES, Condensed Matter Physics

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