BCS-BEC Crossover Effects and Pseudogap in Neutron Matter

Durel, David; Urban, Michael

doi:10.3390/universe6110208

Cited by 9 publications

(6 citation statements)

References 47 publications

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“…The research is driven by developments in the field of ultracold Fermi gas. In the case of spin-symmetric gas, the phase diagram as a function of temperature and interaction strength is well-established, apart from the presence of a pseudogap regime which is still the subject of ongoing discussion [5,6]. In contrast, spin-imbalanced systems lack an undisputed phase diagram [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Disordered structures in ultracold spin-imbalanced Fermi gas

et al. 2023

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We investigate properties of spin-imbalanced ultracold Fermi gas in a large range of spin polarizations at low temperatures. We present results of microscopic calculations based on mean-field and density functional theory approaches, with no symmetry constraints. At low polarization values we predict the structure of the system as consisting of several spin-polarized droplets. As the polarization increases, the system self-organizes into a disordered structure similar to liquid crystals, and energetically they can compete with ordered structures such as grid-like domain walls. At higher polarizations the system starts to develop regularities that, in principle, can be called supersolid, where periodic density modulation and pairing correlations coexist. The robustness of the results has been checked with respect to temperature effects, dimensionality, and the presence of a trapping potential. Dynamical stability has also been investigated.

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Section: Introductionmentioning

confidence: 99%

Disordered structures in ultracold spin-imbalanced Fermi gas

et al. 2023

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“…Moreover, the latest results of the lattice simulations also indicate the existence of the peak of the speed of sound in the crossover regime [16,17]. A similar strong-coupling crossover phenomenon has been extensively studied in cold atomic systems [18][19][20][21][22], where the molecular BEC continuously changes to the BCS-type Cooper pair condensate in a manner accompanied by strong pairing fluctuations [23,24] in two-component Fermi gases. The possible occurrence of the peak of the speed of sound has also been discussed in the density-induced BEC-BCS crossover with the finite-range interaction [25].…”

Section: Introductionmentioning

confidence: 83%

Density-Induced Hadron–Quark Crossover via the Formation of Cooper Triples

et al. 2023

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We discuss the hadron–quark crossover accompanied by the formation of Cooper triples (three-body counterpart of Cooper pairs) by analogy with the Bose–Einstein condensate to Bardeen–Cooper–Schrieffer crossover in two-component fermionic systems. Such a crossover is different from a phase transition, which often involves symmetry breaking. We calculate the in-medium three-body energy from the three-body T-matrix with a phenomenological three-body force characterizing a bound hadronic state in vacuum. With increasing density, the hadronic bound-state pole smoothly undergoes a crossover toward the Cooper triple phase where the in-medium three-body clusters coexist with the quark Fermi sea. The relation to the quarkyonic matter model can also be found in a natural manner.

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“…Corrections due to pair correlations in the normal phase of neutron matter have been considered by several authors [47][48][49][50][51][52] using the Nozières-Schmitt-Rink approach [46], which is the simplest one that interpolates correctly between the BCS and BCE limits. BCS-BEC crossover effects and the existence, above the critical temperature T c for the transition to the superfluid state, of a pseudo-gap in neutron matter have been also recently studied within the in-medium T-matrix formalism by Durel and Urban in reference [53]. At the BCS-BEC transition point, i.e., at the unitary limit, the superfluid pairing gap is expected to be proportional to the free Fermi energy, E F =h 2 k 2 F /2m.…”

Section: Introductionmentioning

confidence: 99%

Low-Density Neutron Matter and the Unitary Limit

Vidaña

2021

Front. Phys.

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We review the properties of neutron matter in the low-density regime. In particular, we revise its ground state energy and the superfluid neutron pairing gap and analyze their evolution from the weak to the strong coupling regime. The calculations of the energy and the pairing gap are performed, respectively, within the Brueckner–Hartree–Fock (BHF) approach of nuclear matter and the Bardeen–Cooper–Schrieffer (BCS) theory using the chiral nucleon-nucleon interaction of Entem and Machleidt at N3LO and the Argonne V18 phenomenological potential. Results for the energy are also shown for a simple Gaussian potential with a strength and range adjusted to reproduce the 1S0 neutron-neutron scattering length and effective range. Our results are compared with those of quantum Monte Carlo (QMC) calculations for neutron matter and cold atoms. The Tan contact parameter in neutron matter is also calculated, finding a reasonable agreement with experimental data from ultra-cold atoms only at very low densities. We find that low-density neutron matter exhibits a behavior close to that of a Fermi gas at the unitary limit, although, this limit is actually never reached. We also review the properties (energy, effective mass, and quasiparticle residue) of a spin-down neutron impurity immersed in a low-density free Fermi gas of spin-up neutrons already studied by the author in a recent work where it was shown that these properties are very close to those of an attractive Fermi polaron in the unitary limit.

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BCS-BEC Crossover Effects and Pseudogap in Neutron Matter

Cited by 9 publications

References 47 publications

Disordered structures in ultracold spin-imbalanced Fermi gas

Disordered structures in ultracold spin-imbalanced Fermi gas

Density-Induced Hadron–Quark Crossover via the Formation of Cooper Triples

Low-Density Neutron Matter and the Unitary Limit

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