Theory for Quartet Condensation in Fermi Systems with Applications to Nuclei and Nuclear Matter

Schuck, Peter; Funaki, Y.; Horiuchi, Hisashi; Röpke, G.; Tohsaki, Akihiro; Yamada, T.

doi:10.1088/1742-6596/529/1/012014

Cited by 4 publications

(5 citation statements)

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“…In the case of quartets, the derivation of a single-particle mass operator is more involved, and we give here only the final expression (for a detailed derivation, see Refs. [461,462]):…”

Section: Quartet Bec With Applications To Nuclear Systems: Alpha Condmentioning

confidence: 99%

The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems

et al. 2018

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This report adresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. By this crossover, the phenomena of Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. This size ranges, from large values when Cooper pairs are strongly overlapping in the BCS limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the BEC limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance.The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultracold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear manybody theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. Common to both contexts is the fact that at zero temperature the BCS-BEC crossover can be described at the mean-field level with reasonable accuracy. At finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient of the theory, especially in the normal phase where they account for precursor pairing effects.After an introduction to present the key concepts of the BCS-BEC crossover, this report discusses the mean-field treatment of the superfluid phase, both for homogeneous and inhomogeneous systems, as well as for symmetric (spinor isospin-balanced) and asymmetric (spin-or isospin-imbalanced) matter. Pairing fluctuations in the normal phase are then considered, with their manifestations in thermodynamic and dynamic quantities. The last two Sections provide a more specialized discussion of the BCS-BEC crossover in ultra-cold Fermi gases and nuclear matter, respectively. The separate discussion in the two contexts aims at cross communicating to both communities topics and aspects which, albeit arising in one of the two fields, share a strong common interest.

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“…In the case of quartets, the derivation of a single-particle mass operator is more involved, and we give here only the final expression (for a detailed derivation, see Refs. [461,462]):…”

Section: Quartet Bec With Applications To Nuclear Systems: Alpha Condmentioning

confidence: 99%

The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems

et al. 2018

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“…The theoretical description of quartet condensation in Fermi systems, with applications to nuclei and nuclear matter, has been discussed in Refs. [88][89][90][91][92].…”

Section: Alpha Particle Condensationmentioning

confidence: 99%

Cold Atoms Beyond Atomic Physics

Madeira

Bagnato

2020

Braz J Phys

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In the last 25 years, much progress has been made producing and controlling Bose-Einstein condensates (BECs) and degenerate Fermi gases. The advances in trapping, cooling, and tuning the interparticle interactions in these cold atom systems lead to an unprecedented amount of control that one can exert over them. This work aims to show that knowledge acquired studying cold atom systems can be applied to other fields that share similarities and analogies with them, provided that the differences are also known and taken into account. We focus on two specific fields: nuclear physics and statistical optics. The nuclear physics discussion occurs with the BCS-BEC crossover in mind, in which we compare cold Fermi gases with nuclear and neutron matter and nuclei. We connect BECs and atom lasers through both systems' matter-wave character for the analogy with statistical optics. Finally, we present some challenges that, if solved, would increase our understanding of cold atom systems and, thus, the related areas.

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“…One of the major advantages of the BCS approach is the possibility of describing the paired system in a picture of weakly interacting "quasiparticles", whose associated operators obey an annihilation condition with respect to the correlated BCS vacuum. Despite its nonlinear character, the above quartet-BCS state still admits a generalized class of annihilation operators, due to its coherent state nature [15]. However, at variance with the linear quasiparticles of the BCS case, the annihilation operators in the quartetting case do not obey simple linear equations of motion.…”

mentioning

confidence: 99%

“…At this point it is worth stressing that the quartet condensation in the pairing context mentioned above should not be confused with the other 'quartet condensate' concept, based on a similar wave function as the QCM one but dealing with in medium bound states of four fermions as, e.g., alpha particles, and their Bose-Einstein condensation [13,14] in finite nuclei and infinite nuclear matter. While no alpha particle condensate survives at saturation density, one may develop a theory for quartet condensation which in many aspects is similar to the BCS approach for the condensation of pairs [15].…”

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confidence: 99%

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Bridging the quartet and pair pictures of isovector proton-neutron pairing

Baran,

Nichita,

Negrea

et al. 2020

Preprint

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The formal implications of a quartet coherent state ansatz for proton-neutron pairing are analyzed. Its nonlinear annihilation operators, which generalize the BCS linear quasiparticle operators, are computed in the quartetting case. Their structure is found to generate nontrivial relationships between the many body correlation functions. The intrinsic structure of the quartet coherent state is detailed, as it hints to the precise correspondence between the quartetting picture and the symmetry restored pair condensate picture for the proton-neutron pairing correlations.

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Theory for Quartet Condensation in Fermi Systems with Applications to Nuclei and Nuclear Matter

Cited by 4 publications

References 66 publications

The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems

The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems

Cold Atoms Beyond Atomic Physics

Bridging the quartet and pair pictures of isovector proton-neutron pairing

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