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Composite bosons in the two-dimensional BCS-BEC crossover from Gaussian fluctuations

  Articoli su Riviste JCR/ISI  (anno 2015)

Autori:  Salasnich L., Toigo F

Affiliazione Autori:  Università di Padova e INO-CNR

Riassunto:  We study Gaussian fluctuations of the zero-temperature attractive Fermi gas in the two-dimensional (2D) BCS-BEC crossover showing that they are crucial to get a reliable equation of state in the Bose-Einstein condensation (BEC) regime of composite bosons, bound states of fermionic pairs. A low-momentum expansion up to the fourth order of the quadratic action of the fluctuating pairing field gives an ultraviolent divergent contribution of the Gaussian fluctuations to the grand potential. Performing dimensional regularization we evaluate the effective coupling constant in the beyond-mean-field grand potential. Remarkably, in the BEC regime our grand potential gives exactly the Popov's equation of state of 2D interacting bosons, and allows us to identify the scattering length aB of the interaction between composite bosons as aB=aF/(21/2e1/4)=0.551...aF, with aF is the scattering length of fermions. Remarkably, the value from our analytical relationship between the two scattering lengths is in full agreement with that obtained by recent Monte Carlo calculations.

Rivista/Giornale:  PHYSICAL REVIEW A
Volume n.:  91      Pagine da: 011604(R)  a: 011604(R)
Collegamento Web del Prodotto: Clicca qui

*Impact Factor della Rivista: (2015) 2.765
data tratti da "WEB OF SCIENCE" (marchio registrato di Thomson Reuters) ed aggiornati a:  19/05/2019

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