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

Abstract

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. Asmore » 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.« less

Authors:
 [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)
Publication Date:
Research Org.:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1247301
Alternate Identifier(s):
OSTI ID: 1210112
Report Number(s):
LA-UR-15-24447
Journal ID: ISSN 1050-2947; PLRAAN
Grant/Contract Number:  
AC02-05CH11231; 61474018; 11335005; 2013CB922000; 2014CB845400; FT130100815; FT140100003; DP140103231; DP140100637; AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review A - Atomic, Molecular, and Optical Physics
Additional Journal Information:
Journal Volume: 92; Journal Issue: 2; Journal ID: ISSN 1050-2947
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BCS-BEC crossover; two-dimensional Fermi gas; quantum fluctuation

Citation Formats

He, Lianyi, Lu, Haifeng, Cao, Gaoqing, Hu, Hui, and Liu, Xia -Ji. Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases. United States: N. p., 2015. Web. doi:10.1103/PhysRevA.92.023620.
He, Lianyi, Lu, Haifeng, Cao, Gaoqing, Hu, Hui, & Liu, Xia -Ji. Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases. United States. https://doi.org/10.1103/PhysRevA.92.023620
He, Lianyi, Lu, Haifeng, Cao, Gaoqing, Hu, Hui, and Liu, Xia -Ji. 2015. "Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases". United States. https://doi.org/10.1103/PhysRevA.92.023620. https://www.osti.gov/servlets/purl/1247301.
@article{osti_1247301,
title = {Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases},
author = {He, Lianyi and Lu, Haifeng and Cao, Gaoqing and Hu, Hui and Liu, Xia -Ji},
abstractNote = {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.},
doi = {10.1103/PhysRevA.92.023620},
url = {https://www.osti.gov/biblio/1247301}, journal = {Physical Review A - Atomic, Molecular, and Optical Physics},
issn = {1050-2947},
number = 2,
volume = 92,
place = {United States},
year = {Fri Aug 14 00:00:00 EDT 2015},
month = {Fri Aug 14 00:00:00 EDT 2015}
}

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Cited by: 74 works
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Works referencing / citing this record:

Fermions in Two Dimensions: Scattering and Many-Body Properties
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Fermi-to-Bose crossover in a trapped quasi-2D gas of fermionic atoms
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Chiral two-dimensional p -wave superfluid from s -wave pairing in the Bose-Einstein-condensate regime
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