Spin-Imbalanced Quasi-Two-Dimensional Fermi Gases

Abstract

We measure the density profiles for a Fermi gas of ${}^6$Li containing $N_1$ spin-up atoms and $N_2$ spin-down atoms, confined in a quasi-two-dimensional geometry. The spatial profiles are measured as a function of spin-imbalance $N_2/N_1$ and interaction strength, which is controlled by means of a collisional (Feshbach) resonance. The measured cloud radii and central densities are in disagreement with mean-field Bardeen-Cooper-Schrieffer theory for a true two-dimensional system. We find that the data for normal-fluid mixtures are reasonably well fit by a simple two-dimensional polaron model of the free energy. Not predicted by the model is a phase transition to a spin-balanced central core, which is observed above a critical value of $N_2/N_1$. Our observations provide important benchmarks for predictions of the phase structure of quasi-two-dimensional Fermi gases.

14 pages, 12 figures

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Cited by in corpus (9)

• Observation of coherent multiorbital polarons in a two-dimensional Fermi gas
• Fate of the Bose polaron at finite temperature
• Visualizing the BEC-BCS crossover in the two-dimensional Fermi gas: pairing gaps and dynamical response functions from ab initio computations
• Larkin-Ovchinnikov superfluidity in a two-dimensional imbalanced atomic Fermi gas
• Thermodynamic equivalence of two-dimensional imperfect attractive Fermi and repulsive Bose gases
• Higher-Harmonic Collective Modes in a Trapped Gas from Second-Order Hydrodynamics
• Kosterlitz-Thouless transition and vortex-antivortex lattice melting in two-dimensional Fermi gases with $p$- or $d$-wave pairing
• Triplet character of 2D-fermion dimers arising from $s$-wave attraction via spin-orbit coupling and Zeeman splitting
• Signatures of the orthogonality catastrophe in a coherently driven impurity