Observation of a Two-Dimensional Fermi Gas of Atoms

Martiyanov, Kirill; Makhalov, Vasiliy; Turlapov, Andrey

doi:10.1103/physrevlett.105.030404

Cited by 201 publications

(245 citation statements)

References 41 publications

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“…As examples of very recent experimental achievements in cold balanced Fermi systems in low dimensions, more specifically in 2D, we highlight the report of the measurement of the density profile and temperature of a 2D gas of atoms [4], pairing in a harmonically trapped 2D atomic Fermi gas in the regime of strong coupling [5], and the detection of a many-body pairing gap above the superfluid transition temperature (the pseudogap phenomenon) [6]. To the best of our knowledge, up to now the only experimental investigations with imbalanced 2D Fermi gases concerns the Fermi polaron problem, in which a single spin-↓ atom interacts strongly with a Fermi sea of spin-↑ atoms [7].…”

Section: Introductionmentioning

confidence: 99%

Finite-temperature phase diagram of quasi-two-dimensional imbalanced Fermi gases beyond mean field

et al. 2012

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We investigate the superfluid transition temperature of quasi-two-dimensional imbalanced Fermi gases beyond the mean-field approximation, through the second-order (or induced) interaction effects. For a balanced Fermi system the transition temperature is suppressed by a factor ≈ 2.72. For imbalanced Fermi systems, the polarization and transition temperature of the tricritical point are significantly reduced as the two-body binding energy |ǫB | increases.

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Section: Introductionmentioning

confidence: 99%

Finite-temperature phase diagram of quasi-two-dimensional imbalanced Fermi gases beyond mean field

et al. 2012

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“…Reducing the dimensionality [9] led to the observation of a Berezinskii-Kosterlitz-Thouless (BKT) type phase transition to a superfluid phase in weakly interacting 2D Bose gases [10,11]. Tuning the strength of interactions in a three-dimensional two-component Fermi gas made it possible to explore the crossover between a molecular Bose-Einstein Condensate (BEC) and a BCS superfluid [12][13][14][15].Recently, efforts have been made to combine reduced dimensionality with the tunability of interactions and to experimentally explore ultracold 2D Fermi gases [16][17][18][19][20][21]. However, the phase transition to a condensed phase has not yet been observed.…”

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confidence: 99%

Observation of Pair Condensation in the Quasi-2D BEC-BCS Crossover

et al. 2015

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The condensation of fermion pairs lies at the heart of superfluidity. However, for strongly correlated systems with reduced dimensionality the mechanisms of pairing and condensation are still not fully understood. In our experiment we use ultracold atoms as a generic model system to study the phase transition from a normal to a condensed phase in a strongly interacting quasi-two-dimensional Fermi gas. Using a novel method, we obtain the in situ pair momentum distribution of the strongly interacting system and observe the emergence of a low-momentum condensate at low temperatures. By tuning temperature and interaction strength we map out the phase diagram of the quasi-2D BEC-BCS crossover.The characteristics of quantum many-body systems are strongly affected by their dimensionality and the strength of interparticle correlations. In particular, strongly correlated two-dimensional fermionic systems have been of interest because of their connection to high-T c superconductivity. Although they have been the subject of intense theoretical studies [1][2][3][4][5][6][7][8], a complete theoretical framework has not yet been established.Ultracold quantum gases are an ideal realization for exploring strongly interacting 2D Fermi gases, as they offer the possibility of independently tuning the dimensionality and the strength of interparticle interactions. Reducing the dimensionality [9] led to the observation of a Berezinskii-Kosterlitz-Thouless (BKT) type phase transition to a superfluid phase in weakly interacting 2D Bose gases [10,11]. Tuning the strength of interactions in a three-dimensional two-component Fermi gas made it possible to explore the crossover between a molecular Bose-Einstein Condensate (BEC) and a BCS superfluid [12][13][14][15].Recently, efforts have been made to combine reduced dimensionality with the tunability of interactions and to experimentally explore ultracold 2D Fermi gases [16][17][18][19][20][21]. However, the phase transition to a condensed phase has not yet been observed. Here, we report on the condensation of pairs of fermions in the quasi-2D BEC-BCS crossover.The BEC-BCS crossover smoothly links a bosonic superfluid of tightly bound diatomic molecules to a fermionic superfluid of Cooper pairs in 2D as well as 3D systems. However, changing the dimensionality leads to some inherent differences. In two dimensions, there is a two-body bound state for all values of the interparticle interaction. Furthermore, because of the enhanced role of * To whom correspondence should be addressed. E-mail: mries@physi.uni-heidelberg.de † These authors contributed equally to this work. ‡ Present address: MIT-Harvard Center for Ultracold Atoms, MIT, Cambridge, MA 02139, USA.fluctuations in 2D, true long-range order is forbidden for homogeneous systems at finite temperature [22,23]. Still, a low temperature superfluid phase with quasi-long-range order can emerge due to the BKT mechanism [24,25]. In a 2D gas with contact interactions, the interactions can be described by the 2D scattering length a 2D . Using th...

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“…In the bottom panel, we plot the effective range integrand in Eq. (18). Here the dotted line simply marks the r-axis.…”

Section: Bound States In 2dmentioning

confidence: 99%

“…In the bottom panel we plot the integrand in Eq. (18), where the effective range is proportional to the square root of the area under each curve. The width parameter is fixed at µ/k F = 100.…”

Section: Bound States In 2dmentioning

confidence: 99%

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Fermions in Two Dimensions: Scattering and Many-Body Properties

et al. 2017

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Ultracold atomic Fermi gases in two-dimensions (2D) are an increasingly popular topic of research. The interaction strength between spin-up and spindown particles in two-component Fermi gases can be tuned in experiments, allowing for a strongly interacting regime where the gas properties are yet to be fully understood. We have probed this regime for 2D Fermi gases by performing T = 0 ab initio diffusion Monte Carlo (DMC) calculations. The many-body dynamics are largely dependent on the two-body interactions, therefore we start with an in-depth look at scattering theory in 2D. We show the partial-wave expansion and its relation to the scattering length and effective range. Then we discuss our numerical methods for determining these scattering parameters. We close out this discussion by illustrating the details of bound states in 2D. Transitioning to the many-body system, we use variationally optimized wave functions to calculate ground-state properties of the gas over a range of interaction strengths. We show results for the energy per particle and parametrize an equation of state. We then proceed to determine the chemical potential for the strongly interacting gas.

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Observation of a Two-Dimensional Fermi Gas of Atoms

Cited by 201 publications

References 41 publications

Finite-temperature phase diagram of quasi-two-dimensional imbalanced Fermi gases beyond mean field

Finite-temperature phase diagram of quasi-two-dimensional imbalanced Fermi gases beyond mean field

Observation of Pair Condensation in the Quasi-2D BEC-BCS Crossover

Fermions in Two Dimensions: Scattering and Many-Body Properties

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