skip to main content

DOE PAGESDOE PAGES

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

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:
OSTI Identifier:
1247301
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
Type:
Accepted Manuscript
Journal Name:
Physical Review. A
Additional Journal Information:
Journal Volume: 92; Journal Issue: 2; Journal ID: ISSN 1050-2947
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
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