Search results for "Pairing"
showing 10 items of 173 documents
Fulde-Ferrell-Larkin-Ovchinnikov pairing in one-dimensional optical lattices
2008
Spin-polarized attractive Fermi gases in one-dimensional (1D) optical lattices are expected to be remarkably good candidates for the observation of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We model these systems with an attractive Hubbard model with population imbalance. By means of the density-matrix renormalization-group method, we compute the pairing correlations as well as the static spin and charge structure factors in the whole range from weak to strong coupling. We demonstrate that pairing correlations exhibit quasi-long-range order and oscillations at the wave number expected from the FFLO theory. However, we also show by numerically computing the mixed spin-charge static …
Superfluidity of fermionic pairs in a harmonic trap. Comparative studies: Local Density Approximation and Bogoliubov-de Gennes solutions
2020
Abstract Experiments with ultracold gases on the lattice give the opportunity to realize superfluid fermionic mixtures in a trapping potential. The external trap modifies the chemical potential locally. Moreover, this trap also introduces non-homogeneity in the superconducting order parameter. There are, among other approaches, two methods which can be used to describe the system of two-component mixtures loaded into an optical lattice: the Local Density Approximation (LDA) and the self-consistent Bogoliubov–de Gennes equations. Here, we compare results obtained within these two methods. We conclude that the results can be distinguishable only in the case of a small value of the pairing int…
Hartree-Fock-Bogoliubov solution of the pairing Hamiltonian in finite nuclei
2013
We present an overview of the Hartree-Fock-Bogoliubov (HFB) theory of nucleonic superfluidity for finite nuclei. After introducing basic concepts related to pairing correlations, we show how the correlated pairs are incorporated into the HFB wave function. Thereafter, we present derivation and structure of the HFB equations within the superfluid nuclear density functional formalism and discuss several aspects of the theory, including the unitarity of the Bogoliubov transformation in truncated single-particle and quasiparticle spaces, form of the pairing functional, structure of the HFB continuum, regularization and renormalization of pairing fields, and treatment of pairing in systems with …
Pairing in a three-component Fermi gas
2006
We consider pairing in a three-component gas of degenerate fermions. In particular, we solve the finite temperature mean-field theory of an interacting gas for a system where both interaction strengths and fermion masses can be unequal. At zero temperature we find a a possibility of a quantum phase transition between states associated with pairing between different pairs of fermions. On the other hand, finite temperature behavior of the three-component system reveals some qualitative differences from the two-component gas: for a range of parameters it is possible to have two different critical temperatures. The lower one corresponds to a transition between different pairing channels, while …
Spatial dependence of the pairing field calculated with bare and induced interactions
2009
The interaction induced by the exchange of low-lying surface vibrations between pairs of orbitals close to the Fermi surface provides an important contribution to pairing correlations in superfluid nuclei. We study the spatial dependence of the pairing field obtained adding the bare and induced interaction in 120Sn.
Preparation and characterization of brass-based coatings
2018
Cold Spray (CS) has been widely investigated owing to its high deposition efficiency and retention of the properties of starting materials. Thus, this process has shown obvious advantages over the fabrication of different copper-based deposits and its alloys over other techniques, such as electroplating, Laser Cladding or thermal spraying. As one of the main copper alloys, brass is implanted in the fields of architecture or industry. Nevertheless, nowadays it is clear that there is very little work on brass coatings, and they were mainly made by electroplating and any other deposition methods, which has severely limits their uses in many applications.This study was applied to develop the br…
The electron gas with a strong pairing interaction: Three particle correlations and the Thouless instability
2000
We derive simplified Faddeev type equations for the three particle T-matrix which are valid in the Hubbard model where only electrons with opposite spins interact. Using the approximation of dynamical mean field theory these equations are partially solved numerically for the attractive Hubbard model. It is shown that the three particle T-matrix contains a term vanishing $\sim T^2$ at the Thouless (or BCS) instability where the two-particle T-matrix diverges. Based on the three particle term we further derive the low density - strong coupling extension for the two-particle vertex function. We therefore understand our equations as a step towards a systematic low density expansion from the wea…
DNA oxidation products determined with repair endonucleases in mammalian cells: Types, basal levels and influence of cell proliferation
1999
Purified repair endonucleases such as Fpg protein, endonuclease III and IV allow a very sensitive quantification of various types of oxidative DNA modifications in mammalian cells. By means of these assays, the numbers of base modifications sensitive to Fpg protein, which include 8-hydroxyguanine (8-oxoG), were determined to be less than 0.3 per 10(6) bp in several types of untreated cultured mammalian cells and human lymphocytes and less than 10 per 10(6) bp in mitochondrial DNA from rat and porcine liver. Oxidative 5,6-dihydropyrimidine derivatives sensitive to endonuclease III and sites of base loss sensitive to endonuclease IV or exonuclease III were much less frequent than Fpg-sensitiv…
Mixed-valence polyoxometalate clusters. II. Delocalization of electronic pairs in 18-site heteropoly blues with Wells-Dawson structure
1995
Abstract The problem of delocalization of two electrons in the 18-site Wells-Dawson polyoxometalate is examined from a general approach that takes into account both single- and double-transfer processes, as well as the Coulomb interactions between the two delocalized electrons. The electronic energy levels of this mixed-valence cluster are calculated and the conditions giving rise to the stabilization of a singlet ground spin state for the electronic pair are elucidated. It is shown that the spin pairing results from the simultaneous effects of single- and double-electron transfer processes, which are operative even when the two delocalized electrons are fairly widely separated in the Wells…
Binding energies and pairing gaps in semi-magic nuclei obtained using new regularized higher-order EDF generators
2016
We present results of the Hartree-Fock-Bogolyubov calculations performed using nuclear energy density functionals based on regularized functional generators at next-to-leading and next-to-next-to-leading order. We discuss properties of binding energies and pairing gaps determined in semi-magic spherical nuclei. The results are compared with benchmark calculations performed for the functional generator SLyMR0 and functional UNEDF0.