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Unlike the Coulomb potential that acts between all semiconductor carriers, the potential commonly used for BCS superconductors and cold atom gases acts between different fermion species only, these species differing by their spin or…

Quantum Gases · Physics 2016-02-03 Monique Combescot , Shiue-Yuan Shiau , Yia-Chung Chang

We use Richardson-Gaudin exact equations to derive the ground-state energy of $N$ composite bosons (cobosons) interacting via a potential which acts between fermion pairs having zero center-of-mass momentum, that is, a potential similar to…

Quantum Gases · Physics 2016-12-13 Shiue-Yuan Shiau , Monique Combescot , Yia-Chung Chang

We derive the ground-state energy of $N$ composite bosons made of fermion pairs using the recently developed composite boson many-body formalism. We concentrate on the $N$-pair energy linear in density. We show that the scattering relevant…

Strongly Correlated Electrons · Physics 2015-06-15 Shiue-Yuan Shiau , Yia-Chung Chang , Monique Combescot

This Letter provides the solution to a yet unsolved basic problem of Solid State Physics: the ground state energy of an arbitrary number of Cooper pairs interacting via the Bardeen-Cooper-Schrieffer potential. We here break a 50 year old…

Superconductivity · Physics 2011-11-28 Michel Crouzeix , Monique Combescot

We derive the scattering length of composite bosons (cobosons) within the framework of the composite boson many-body formalism that uses correlated-pair states as a basis, instead of free fermion states. The integral equation constructed…

Quantum Gases · Physics 2016-12-01 Shiue-Yuan Shiau , Monique Combescot , Yia-Chung Chang

We extend the one-pair Cooper configuration towards Bardeen-Cooper-Schrieffer (BCS) model of superconductivity by adding one-by-one electron pairs to an energy layer where a small attraction acts. To do it, we solve Richardson's equations…

Superconductivity · Physics 2015-05-27 W. V. Pogosov , M. Combescot

We consider the development of Cooper pairs in a self-consistent Hartree Fock mean field for the even Sm isotopes. Results are presented at the level of a BCS treatment, a number-projected BCS treatment and an exact treatment using the…

Nuclear Theory · Physics 2008-11-26 G. G. Dussel , S. Pittel , J. Dukelsky , P. Sarriguren

Particles made of two fermions can in many cases be treated as elementary bosons, but the conditions for this treatment to be valid are nontrivial. The so-called "coboson formalism" is a powerful tool to tackle compositeness effects…

Quantum Gases · Physics 2022-01-06 E. Cuestas , C. Cormick

The purpose of this paper is to show how the diagrammatic expansion in fermion exchanges of scalar products of $N$-composite-boson (``coboson'') states can be obtained in a practical way. The hard algebra on which this expansion is based,…

Statistical Mechanics · Physics 2007-05-23 M. Combescot , O. Betbeder-Matibet

The understanding of the behaviour of systems of identical composite bosons has progressed significantly in connection with the analysis of the entanglement between constituents and the development of coboson theory. The basis of these…

A theoretical methodology for exploring the conventional Bardeen-Cooper-Schrieffer (BCS) pairing instability for superconductivity from a correlated normal phase for all possible degrees of many-body correlation, has been developed. The…

Superconductivity · Physics 2021-02-24 Koushik Mandal , Ranjan Chaudhury

We have recently constructed a many-body theory for composite excitons, in which the possible carrier exchanges between $N$ excitons can be treated exactly through a set of dimensionless ``Pauli scatterings'' between two excitons. Many-body…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 M. Combescot , O. Betbeder-Matibet , F. Dubin

By introducing a set of auxiliary equations representing a many-body system, we have derived an extension of the Kohn-Sham scheme for the density functional theory. These equations consist of a Kohn-Sham-type equation determining…

Materials Science · Physics 2009-11-07 Koichi Kusakabe

A new theory for Cooper pair formation and superconductivity is derived from quantum statistical mechanics. It is shown that zero momentum Cooper pairs have non-local permutations and behave as effective bosons with an internal weight close…

Superconductivity · Physics 2022-04-04 Phil Attard

We analyze a system of fermions in a one-dimensional harmonic trap with attractive delta-interactions between different fermions species, as an approximate description of experiments involving atomic dimers. We solve the problem of two…

Quantum Gases · Physics 2023-01-11 Martín D. Jiménez , Eloisa Cuestas , Ana P. Majtey , Cecilia Cormick

The use of exactly-solvable Richardson-Gaudin (R-G) models to describe the physics of systems with strong pair correlations is reviewed. We begin with a brief discussion of Richardson's early work, which demonstrated the exact solvability…

Nuclear Theory · Physics 2008-11-26 J. Dukelsky , S. Pittel , G. Sierra

The Bogoliubov approach to superconductivity provides a strong mathematical support to the wave function ansatz proposed by Bardeen, Cooper and Schrieffer (BCS). Indeed, this ansatz --- with all pairs condensed into the same state ---…

Superconductivity · Physics 2015-06-03 M. Combescot , W. V. Pogosov , O. Betbeder-Matibet

Using the Bethe-Salpeter (BS) equation, Cooper pairing can be generalized to include contributions from holes as well as particles from the ground state of either an ideal Fermi gas (IFG) or of a BCS many-fermion state. The BCS model…

Superconductivity · Physics 2009-11-07 M. Fortes , M. A. Solis , M. de Llano , V. V. Tolmachev

In a recent paper we studied the behavior of the pairing gaps $\Delta_F$ as a function of the Fermi momentum $k_F$ for neutron and nuclear matter in all relevant angular momentum channels where superfluidity is believed to naturally emerge.…

Nuclear Theory · Physics 2014-12-01 P. Finelli , S. Maurizio , J. W. Holt

Cooper pairing in two dimensions is analyzed with a set of renormalized equations to determine its binding energy for any fermion number density and all coupling assuming a generic pairwise residual interfermion interaction. \ Also…

Superconductivity · Physics 2016-08-15 S. K. Adhikari , M. Casas , A. Puente , A. Rigo , M. Fortes , M. A. Solís , M. de Llano , A. A. Valladares , O. Rojo
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