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Title: Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases

Journal Article · · Physical Review A - Atomic, Molecular, and Optical Physics
 [1];  [2];  [3];  [4];  [4]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Electronic Science and Technology of China, Chengdu (China)
  3. Tsinghua Univ., Beijing (China)
  4. Swinburne Univ. of Technology, Melbourne (Australia)

We present a theoretical study of the ground state of the BCS-BEC crossover in dilute two-dimensional Fermi gases. While the mean-field theory provides a simple and analytical equation of state, the pressure is equal to that of a noninteracting Fermi gas in the entire BCS-BEC crossover, which is not consistent with the features of a weakly interacting Bose condensate in the BEC limit and a weakly interacting Fermi liquid in the BCS limit. The inadequacy of the two-dimensional mean-field theory indicates that the quantum fluctuations are much more pronounced than those in three dimensions. In this work, we show that the inclusion of the Gaussian quantum fluctuations naturally recovers the above features in both the BEC and the BCS limits. In the BEC limit, the missing logarithmic dependence on the boson chemical potential is recovered by the quantum fluctuations. Near the quantum phase transition from the vacuum to the BEC phase, we compare our equation of state with the known grand canonical equation of state of two-dimensional Bose gases and determine the ratio of the composite boson scattering length aB to the fermion scattering length a2D. We find aB ≃ 0.56a2D, in good agreement with the exact four-body calculation. As a result, we compare our equation of state in the BCS-BEC crossover with recent results from the quantum Monte Carlo simulations and the experimental measurements and find good agreements.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-05CH11231; 61474018; 11335005; 2013CB922000; 2014CB845400; FT130100815; FT140100003; DP140103231; DP140100637; AC52-06NA25396
OSTI ID:
1247301
Alternate ID(s):
OSTI ID: 1210112
Report Number(s):
LA-UR-15-24447; PLRAAN
Journal Information:
Physical Review A - Atomic, Molecular, and Optical Physics, Vol. 92, Issue 2; ISSN 1050-2947
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 74 works
Citation information provided by
Web of Science

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Cited By (21)

Fermions in Two Dimensions: Scattering and Many-Body Properties journal August 2017
Fermi-to-Bose crossover in a trapped quasi-2D gas of fermionic atoms journal August 2017
Quantum fluctuations in a strongly interacting Bardeen-Cooper-Schrieffer polariton condensate at thermal equilibrium journal January 2020
Chiral two-dimensional p -wave superfluid from s -wave pairing in the Bose-Einstein-condensate regime journal January 2020
Theory of strongly paired fermions with arbitrary short-range interactions journal January 2020
Diffusion Monte Carlo study of strongly interacting two-dimensional Fermi gases journal February 2016
Strongly correlated Fermi superfluid near an orbital Feshbach resonance: Stability, equation of state, and Leggett mode journal October 2016
Dimensional crossover in a strongly interacting ultracold atomic Fermi gas journal October 2017
Visualizing the BEC-BCS crossover in a two-dimensional Fermi gas: Pairing gaps and dynamical response functions from ab initio computations journal December 2017
Strongly interacting Sarma superfluid near orbital Feshbach resonances journal April 2018
Effect of weak disorder on the BCS–BEC crossover in a two-dimensional Fermi gas journal April 2017
Going beyond the BCS level in the superfluid path integral: A consistent treatment of electrodynamics and thermodynamics journal May 2016
Equation of State of Ultracold Fermions in the 2D BEC-BCS Crossover Region text January 2015
Diffusion Monte Carlo study of strongly interacting two-dimensional Fermi gases text January 2015
Strongly correlated Fermi superfluid near an orbital Feshbach resonance: Stability, equation of state and Leggett mode text January 2016
Pressure profiles of nonuniform two-dimensional atomic Fermi gases text January 2016
Effect of Weak Disorder on the BCS-BEC crossover in a two-dimensional Fermi Gas text January 2016
Dimensional crossover in a strongly interacting ultracold atomic Fermi gas text January 2017
Visualizing the BEC-BCS crossover in the two-dimensional Fermi gas: pairing gaps and dynamical response functions from ab initio computations text January 2017
A strongly interacting Sarma superfluid near orbital Feshbach resonances text January 2018
Theory of strongly paired fermions with arbitrary short-range interactions text January 2019

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