Evolution of Cooper pairs with zero-center-of-mass momentum and their first-order correlation function in a two-dimensional ultracold Fermi gas near the observed Berezinskii-Kosterlitz-Thouless transition

Abstract

We investigate the center-of-mass momentum distribution $n_{\mathbf{Q}}$ of Cooper pairs and their first-order correlation function $g_1(r)$ in a strongly interacting two-dimensional Fermi gas. Recently, the BKT (Berezinskii-Kosterlitz-Thouless) transition was reported in a two-dimensional ${}^6$Li Fermi gas, based on (1) the observations of anomalous enhancement of $n_{\mathbf{Q}=0}$ [M. G. Ries, et. al., Phys. Rev. Lett. 114, 230401 (2015)], as well as (2) a power-law behavior of $g_1(r)$ [P. A. Murthy, et. al., Phys. Rev. Lett. 115, 010401 (2015)]. However, including pairing fluctuations within a $T$-matrix approximation (TMA), we show that these results can still be explained as strong-coupling properties of a normal-state two-dimensional Fermi gas. Our results indicate the importance of further experimental observations, to definitely confirm the realization of the BKT transition in this system. Since the BKT transition has been realized in a two-dimensional ultracold Bose gas, our results would be useful for the achievement of this quasi-long range order in an ultracold Fermi gas.

22 pages, 7 figures

References in corpus (22)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• Crossover from a molecular Bose-Einstein condensate to a degenerate Fermi gas
• Resonantly-paired fermionic superfluids
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• Radiofrequency spectroscopy of a strongly interacting two-dimensional Fermi gas
• Superfluid behaviour of a two-dimensional Bose gas
• Observation of the Berezinskii-Kosterlitz-Thouless Phase Transition in an Ultracold Fermi Gas
• Observation of pair condensation in the quasi-2D BEC-BCS crossover
• Vortex proliferation in the Berezinskii-Kosterlitz-Thouless regime on a two-dimensional lattice of Bose-Einstein condensates
• Pseudo-gap pairing in ultracold Fermi atoms
• Enhanced paraconductivity-like fluctuations in the radio frequency spectra of ultracold Fermi atoms
• Matter wave Fourier optics with a strongly interacting two-dimensional Fermi gas
• The effect of population imbalance on the Berezinskii-Kosterlitz-Thouless phase transition in a superfluid Fermi gas
• Pairing effects in the normal phase of a two-dimensional Fermi gas
• Pseudogap and preformed pairs in the imbalanced Fermi gas in two dimensions
• Comparison of strong-coupling theories for a two-dimensional Fermi gas
• Pairing and radio-frequency spectroscopy in two-dimensional Fermi gases
• Quasi-two-dimensional Fermi gases at finite temperature
• Quasi-condensation in two-dimensional Fermi gases
• Pseudogap phenomena in a two-dimensional ultracold Fermi gas near the Berezinskii-Kosterlitz-Thouless transition
• Momentum distribution of Cooper-pairs and strong-coupling effects in a two-dimensional Fermi gas near the Berezinskii-Kosterlitz-Thouless transition

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• Second sound in 2D Bose gas: from the weakly interacting to the strongly interacting regime
• Dynamical structure factors of a two-dimensional Fermi superfluid within random phase approximation
• Vortices and antivortices in two-dimensional ultracold Fermi gases
• Precision Many-Body Study of the Berezinskii-Kosterlitz-Thouless Transition and Temperature-Dependent Properties in the Two-Dimensional Fermi Gas
• Quantum fluctuations and vortex-antivortex unbinding in the 2D BCS-BEC crossover
• Pseudogap regime of a two-dimensional uniform Fermi gas
• Pseudogap phenomena near the BKT transition of a two-dimensional ultracold Fermi gas in the crossover region
• Quantitative Studies on the Quantum Critical Regime near Superfluid to Mott Insulator Transition