Mixtures of ultracold fermions with unequal masses

Iskin, M.; Melo, C. A. R. Sá de

doi:10.1103/physreva.76.013601

Cited by 61 publications

(103 citation statements)

References 42 publications

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“…The scattering between atoms and weakly-bound dimers was first investigated by Skorniakov and TerMartirosian (1956) in connection with neutron-deuteron scattering and, more recently, by Petrov (2003) in the context of degenerate Fermi gases (see also Brodsky et al, 2006;Levinsen and Gurarie, 2006;Iskin and Sá de Melo, 2007b). The solution of the three-body Schrödinger equation for a pair of like fermions interacting with a third particle can be obtained exactly using the contact boundary condition (17) between particles with different spin.…”

Section: Interacting Dimersmentioning

confidence: 99%

“…IV E) should depend on the molecular mass, M = m ↑ + m ↓ , rather than on the reduced mass. Other interesting scenarios, not addressed in this review, refer to the interplay between unequal masses and unequal populations of the two spin components (see, e.g., Iskin and Sá de Melo, 2006b;Parish et al, 2007b;Iskin and Sá de Melo, 2007a). The experimental realization of fermionic heteronuclear mixtures in the strongly correlated regime is at present actively pursued in different laboratories (see, e.g., Wille et al, 2007).…”

Section: Fermi Superfluids With Unequal Massesmentioning

confidence: 99%

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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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Section: Interacting Dimersmentioning

confidence: 99%

Section: Fermi Superfluids With Unequal Massesmentioning

confidence: 99%

Theory of ultracold atomic Fermi gases

2008

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“…For the mass-imbalanced case such an approach was pursued in Ref. [166]. However, to treat (nonlocal) supersolid phases in the trap we need theories that go beyond LDA.…”

Section: Mass-imbalanced Casementioning

confidence: 99%

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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“…Usually, the external confinement is taken into account using the local density approximation, i.e. assuming that the local properties can be described by the non-confined system ones for the local chemical potential [17][18][19]. On the other hand, this assumption usually breaks down when the fermionic density p-1 arXiv:1112.1154v1 [cond-mat.quant-gas] 6 Dec 2011 L /2M is the recoil energy [11].…”

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confidence: 99%

“…The BKT temperature can be estimated by expanding the preceding formula at the gaussian level [6,17,18,33]:…”

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confidence: 99%

Pairing properties of cold fermions in a honeycomb lattice

Grémaud¹

2012

EPL

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-The pairing properties of ultracold fermions, with an attractive interaction, loaded in a honeycomb (graphene-like) optical lattice are studied in a mean-field approach. We emphasize, in the presence of a harmonic trap, the unambiguous signatures of the linear dispersion relation of the band structure around half-filling (i.e. the massless Dirac fermions) in the local order parameter, in particular in the situations of either imbalance hoping parameters or imbalance populations. It can also be observed in the system response to external perturbation, for instance by measuring the pair destruction rate when modulating the optical lattice depth. Going beyond the mean-field level, we estimate the critical temperature for the "condensation" of the preformed pairs.Since its first experimental observation, graphene has attracted considerable attention due to its interest in fundamental physics as well as for potential applications [1,2]. In particular, the energy band spectrum depicts "conical points" where the valence and conduction bands are connected, and the Fermi energy at half-filling is therefore only made of points. Around these points, the energy varies proportionally to the modulus of the wave-vector and the excitations (holes or particles) of the system are equivalent to ultra-relativistic (massless) Dirac fermions since their dispersion relation is linear [3]. In the presence of interaction, the vanishing density of states at the Fermi energy leads to extremely rich physics. Contrary to the square lattice, where the nesting of the Fermi surface generally leads to ordered phases even for arbitrarily small interaction strengths, the Fermi-Hubbard model on the honeycomb lattice depicts two quantum phases transitions at half-filling [4]: first, for weak interaction, one observes a semi-metallic behavior with Dirac-like excitations [5][6][7] similar to the non-interacting situation; for an interaction strength U ≈ 3.5J, the system enters into a spin-liquid phase, i.e. a Mott-Insulator (charge gap) without longrange magnetic ordering [8,9]; eventually, for larger interaction strength U ≈ 4.3J, anti-ferromagnetic order sets in.

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Mixtures of ultracold fermions with unequal masses

Cited by 61 publications

References 42 publications

Theory of ultracold atomic Fermi gases

Theory of ultracold atomic Fermi gases

Imbalanced Fermi gases at unitarity

Pairing properties of cold fermions in a honeycomb lattice

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