Quantum Monte Carlo simulations of the BCS-BEC crossover at finite temperature

Aurel Bulgac, Joaquín E. Drut, and Piotr Magierski
Phys. Rev. A 78, 023625 – Published 21 August 2008

Abstract

The quantum Monte Carlo method for spin-12 fermions at finite temperature is formulated for dilute systems with an s-wave interaction. The motivation and the formalism are discussed along with descriptions of the algorithm and various numerical issues. We report on results for the energy, entropy, and chemical potential as a function of temperature. We give upper bounds on the critical temperature Tc for the onset of superfluidity, obtained by studying the finite-size scaling of the condensate fraction. All of these quantities were computed for couplings around the unitary regime in the range 0.5(kFa)10.2, where a is the s-wave scattering length and kF is the Fermi momentum of a noninteracting gas at the same density. In all cases our data are consistent with normal Fermi gas behavior above a characteristic temperature T0>Tc, which depends on the coupling and is obtained by studying the deviation of the caloric curve from that of a free Fermi gas. For Tc<T<T0 we find deviations from normal Fermi gas behavior that can be attributed to pairing effects. Low-temperature results for the energy and the pairing gap are shown and compared with Green-function Monte Carlo results by other groups.

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  • Received 21 March 2008

DOI:https://doi.org/10.1103/PhysRevA.78.023625

©2008 American Physical Society

Authors & Affiliations

Aurel Bulgac1, Joaquín E. Drut1,*, and Piotr Magierski2

  • 1Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA
  • 2Faculty of Physics, Warsaw University of Technology, ulica Koszykowa 75, 00-662 Warsaw, Poland

  • *Current address: Department of Physics, The Ohio State University, Columbus, OH 43210, USA.

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Vol. 78, Iss. 2 — August 2008

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