Metastability in Spin-Polarized Fermi Gases

Liao, Yunxiang; Revelle, Melissa; Paprotta, Tobias; Rittner, Ann Sophie C.; Li, Wenhui; Partridge, Guthrie B.; Hulet, R. G.

doi:10.1103/physrevlett.107.145305

Cited by 25 publications

(34 citation statements)

References 32 publications

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“…The latest experiments by the group at Rice indicate that their deviating experimental results are caused by spin currents in the trap that create a long lived metastable state with a deformed superfluid core [78]. These experiments confirm the theoretical proposal of Parish and Huse [151], who showed that this metastable state could arise due to the elongated trap geometry, in which evaporation occurs predominantly from the trap center.…”

Section: Experimental Overviewsupporting

confidence: 65%

“…Later, the imbalanced atomic Fermi gas was also experimentally studied at ENS, where Nascimbène et al accurately measured the collective modes [73] and the equation of state of the imbalanced Fermi gas [74,75]. In most recent experimental studies, also nonequilibrium aspects of the imbalanced Fermi gas are considered, such as spin transport [76,77] and metastable states [78].…”

Section: This Reviewmentioning

confidence: 99%

“…It turns out that the resulting evaporative depolarization of the central core stabilizes superfluidity, and thus favors the superfluid phase over the normal phase, even when the overall polarization of the gas is above the expected critical imbalance. The suppression of transport across the interface allows the non-equilibrium density distribution to remain metastable with observed lifetimes of multiple seconds [78]. Although spin transport is an interesting topic that is currently actively being studied experimentally for imbalanced Fermi gases [76,77], we treat in this review only the equilibrium case.…”

Section: Experimental Overviewmentioning

confidence: 99%

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Imbalanced Fermi gases at unitarity

2013

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We consider imbalanced Fermi gases with strong attractive interactions, for which Cooper-pair formation plays an important role. The two-component mixtures consist either of identical fermionic atoms in two different hyperfine states, or of two different atomic species both occupying only a single hyperfine state. In both cases, the number of atoms for each component is allowed to be different, which leads to a spin imbalance, or spin polarization. Two different atomic species also lead to a mass imbalance. Imbalanced Fermi gases are relevant to condensed-matter physics, nuclear physics and astroparticle physics. They have been studied intensively in recent years, following their experimental realization in ultracold atomic Fermi gases. The experimental control in such a system allows for a systematic study of the equation of state and the phase diagram as a function of temperature, spin polarization and interaction strength. In this review, we discuss the progress in understanding strongly-interacting imbalanced Fermi gases, where a main goal is to describe the results of the highly controlled experiments. We start by discussing Feshbach resonances, after which we treat the imbalanced Fermi gas in mean-field theory to give an introduction to the relevant physics. We encounter several unusual superfluid phases, including phase-separation, gapless Sarma superfluidity, and supersolidity. To obtain a more quantitative description of the experiments, we review also more sophisticated techniques, such as diagrammatic methods and the renormalization-group theory. We end the review by discussing two theoretical approaches to treat the inhomogeneous imbalanced Fermi gas, namely the Landau-Ginzburg theory and the Bogoliubov-de Gennes approach.

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Section: Experimental Overviewsupporting

confidence: 65%

Section: This Reviewmentioning

confidence: 99%

Section: Experimental Overviewmentioning

confidence: 99%

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Imbalanced Fermi gases at unitarity

2013

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“…Observations of phase separation in spin-imbalanced Fermi gases were obtained at Rice and MIT by direct in-situ imaging of the density distributions [17][18][19], and by imaging the distributions in time-of-flight [20]. The distributions in the Rice experiment were out-of-equilibrium due to an evaporative depolarization mechanism at work in their highly elongated confining potential [21,22], and could not, therefore, be compared with distributions calculated assuming equilibrium. Density profiles obtained by the MIT group at unitarity and on the BEC side of resonance [23] agree quantitatively with the theory of Bertaina and Giorgini (BG) computed using quantum Monte Carlo (QMC) and the LDA [24].…”

mentioning

confidence: 99%

Phase diagram of a strongly interacting spin-imbalanced Fermi gas

Olsen¹,

Revelle²,

Fry³

et al. 2015

Phys. Rev. A

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We obtain the phase diagram of spin-imbalanced interacting Fermi gases from measurements of density profiles of 6 Li atoms in a harmonic trap. These results agree with, and extend, previous experimental measurements. Measurements of the critical polarization at which the balanced superfluid core vanishes generally agree with previous experimental results and with quantum Monte Carlo (QMC) calculations in the BCS and unitary regimes. We disagree with the QMC results in the BEC regime, however, where the measured critical polarizations are greater than theoretically predicted. We also measure the equation of state in the crossover regime for a gas with equal numbers of the two fermion spin states.

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“…The experiments on the phase diagram of polarized 1 Fermi gases done at MIT [13][14][15] and Paris [16] can be well understood within the LDA. Only in an experiment at Rice University [17], clear deviations from LDA were observed, but they were later shown to correspond to a metastable non-equilibrium configuration of the atomic cloud [18,19].…”

Section: Introductionmentioning

confidence: 99%

Polarized Fermi gases at finite temperature in the BCS-BEC crossover

2014

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We consider a polarized Fermi gas in the BCS-BEC crossover region above the critical temperature within a T matrix formalism. By treating the mean-field like shift of the quasiparticle energies in a self-consistent manner, we avoid the known pathological behavior of the standard Nozières-Schmitt-Rink approach in the polarized case, i.e., the polarization has the right sign and the spin polarizability is positive. The momentum distributions of the correlated system are computed and it is shown that, in the zero-temperature limit, they satisfy the Luttinger theorem. Results for the phase diagram, the spin susceptibility, and the compressibility are discussed.

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Metastability in Spin-Polarized Fermi Gases

Cited by 25 publications

References 32 publications

Imbalanced Fermi gases at unitarity

Imbalanced Fermi gases at unitarity

Phase diagram of a strongly interacting spin-imbalanced Fermi gas

Polarized Fermi gases at finite temperature in the BCS-BEC crossover

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