Surface Tension in Unitary Fermi Gases with Population Imbalance

Silva, Theja N. De; Mueller, Erich J.

doi:10.1103/physrevlett.97.070402

Cited by 89 publications

(108 citation statements)

References 44 publications

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“…Also at Rice University a further study was performed, where Partridge et al observed a deformation of the superfluid core at their lowest temperatures [71]. This deformation was explained in terms of a first-order interface between the superfluid core and the normal outer region in the trap [144,149], see also Fig. 8(c).…”

Section: Experimental Overviewmentioning

confidence: 92%

“…4), where the atom number in each of the two states could be precisely tuned. Within a few months time these experiments were followed by a large amount of theoretical studies, which studied the imbalanced Fermi gas using mean-field approaches [100,135,136,137,138,85], using thermodynamic approaches [139,140], using diagrammatic approaches [141], using the Bogoliubov-de Gennes approach [142,143], including the effects of surface tension [144], including the gradient energy of the density profiles [145], and including Gaussian order parameter fluctuations [146]. The interesting aspect of a polarization in the system is that not all atoms can find a partner to pair up with, because the fermions only have attractive s-wave interactions when they are in different hyperfine states.…”

Section: Experimental Overviewmentioning

confidence: 99%

“…Since we are studying the superfluid-normal interface beyond the LDA, we can determine the surface tension of the calculated interface [144]. The surface tension is the work per unit area that has to be done to increase the area of the interface.…”

Section: Surface Tensionmentioning

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 Overviewmentioning

confidence: 92%

Section: Experimental Overviewmentioning

confidence: 99%

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Imbalanced Fermi gases at unitarity

2013

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“…The non monotonic structure of the density observed in the Rice experiment can be explained through the inclusion of surface tension effects. For a recent discussion of surface tension and thermal effects in spin imbalanced configurations see De Silva and Mueller (2006b), Partridge et al (2006b) and Haque and Stoof (2007).…”

Section: Phase Separation In Harmonic Traps At Unitaritymentioning

confidence: 99%

Theory of ultracold atomic Fermi gases

2008

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The physics of quantum degenerate atomic Fermi gases in uniform as well as in harmonically trapped configurations is reviewed from a theoretical perspective. Emphasis is given to the effect of interactions which play a crucial role, bringing the gas into a superfluid phase at low temperature. In these dilute systems interactions are characterized by a single parameter, the s-wave scattering length, whose value can be tuned using an external magnetic field near a broad Feshbach resonance. The BCS limit of ordinary Fermi superfluidity, the Bose-Einstein condensation (BEC) of dimers and the unitary limit of large scattering length are important regimes exhibited by interacting Fermi gases. In particular the BEC and the unitary regimes are characterized by a high value of the superfluid critical temperature, of the order of the Fermi temperature. Different physical properties are discussed, including the density profiles and the energy of the ground-state configurations, the momentum distribution, the fraction of condensed pairs, collective oscillations and pair breaking effects, the expansion of the gas, the main thermodynamic properties, the behavior in the presence of optical lattices and the signatures of superfluidity, such as the existence of quantized vortices, the quenching of the moment of inertia and the consequences of spin polarization. Various theoretical approaches are considered, ranging from the mean-field description of the BCS-BEC crossover to non-perturbative methods based on quantum Monte Carlo techniques. A major goal of the review is to compare the theoretical predictions with the available experimental results.

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“…Such a phase-separation scenario had been proposed by Clogston [27] and Chandrasekhar [28] long ago, who predicted the occurrence of a first-order transition from the N to the SF state. Since the existence of a N-SF interface may settle some important questions regarding polarized Fermi mixtures, serious research has been focused on this subject [29][30][31]33]. In particular, it has been established [30,31] that a temperature difference between the two phases can appear as a consequence of the blockage of energy transfer across the N-SF interface.…”

Section: Introductionmentioning

confidence: 99%

Linear response of heat conductivity of normal–superfluid interface of a polarized Fermi gas to orbital magnetic field

Ebrahimian

Mehrafarin

Afzali

2012

Physica B: Condensed Matter

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Using perturbed Bogoliubov equations, we study the linear response to a weak orbital magnetic field of the heat conductivity of the normal-superfluid interface of a polarized Fermi gas at sufficiently low temperature. We consider the various scattering regions of the BCS regime and analytically obtain the transmission coefficients and the heat conductivity across the interface in an arbitrary weak orbital field. For a definite choice of the field, we consider various values of the scattering length in the BCS range and numerically obtain the allowed values of the average and species-imbalance chemical potentials. Thus, taking Andreev reflection into account, we describe how the heat conductivity is affected by the field and the species imbalance. In particular, we show that the additional heat conductivity due to the orbital field increases with the species imbalance, which is more noticeable at higher temperatures. Our results indicate how the heat conductivity may be controlled, which is relevant to sensitive magnetic field sensors/regulators at the interface.

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Surface Tension in Unitary Fermi Gases with Population Imbalance

Cited by 89 publications

References 44 publications

Imbalanced Fermi gases at unitarity

Imbalanced Fermi gases at unitarity

Theory of ultracold atomic Fermi gases

Linear response of heat conductivity of normal–superfluid interface of a polarized Fermi gas to orbital magnetic field

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