On-Site Correlation in Narrow Band Materials

1997 ◽  
Vol 491 ◽  
Author(s):  
F. Manghi ◽  
V. Bellini ◽  
M. Rontani ◽  
C. Arcangeli
Keyword(s):  
Configuration Interaction ◽  
Single Particle ◽  
Narrow Band ◽  
Mean Field ◽  
Correlation Effects ◽  
Many Body ◽  
Quasi Particle ◽  
Hubbard Hamiltonian ◽  
Interaction Scheme ◽  
The Many

ABSTRACTWe present the results of a recently developed approach where the interplay between the itinerant and localized character of electrons in narrow band materials is described by adding on-site correlation effects to a realistic band calculation: the single particle band states are treated as mean field solutions of a multi-orbital Hubbard Hamiltonian and the many-body term associated with localized e-e interaction is described in a configuration-interaction scheme. Quasi-particle states of nickel and CuGe03 have been calculated and compared with spectroscopical results.

Role of the second nearest-neighbor hoppings in a disordered Bose–Hubbard Hamiltonian in the Many-Body Localization

2020 ◽  
Vol 93 (9) ◽  
Author(s):  
Edith Djoukouo Ngueyounou ◽  
Kanabet Yapara ◽  
Celsus Bouri ◽  
Hugues Merlain Tetchou Nganso ◽  
Moïse Godfroy Kwato Njock
Keyword(s):  
Nearest Neighbor ◽  
Many Body ◽  
Hubbard Hamiltonian ◽  
The Many

scholarly journals Solvable Model of a Generic Driven Mixture of Trapped Bose–Einstein Condensates and Properties of a Many-Boson Floquet State at the Limit of an Infinite Number of Particles

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1342
Author(s):  
Ofir E. Alon
Keyword(s):  
Angular Momentum ◽  
Infinite Number ◽  
Mean Field ◽  
Solvable Model ◽  
Time Dependent ◽  
Angular Momentum Operator ◽  
Many Body ◽  
The Many ◽  
Bose Einstein ◽  
Number Of Particles

A solvable model of a periodically driven trapped mixture of Bose–Einstein condensates, consisting of N1 interacting bosons of mass m1 driven by a force of amplitude fL,1 and N2 interacting bosons of mass m2 driven by a force of amplitude fL,2, is presented. The model generalizes the harmonic-interaction model for mixtures to the time-dependent domain. The resulting many-particle ground Floquet wavefunction and quasienergy, as well as the time-dependent densities and reduced density matrices, are prescribed explicitly and analyzed at the many-body and mean-field levels of theory for finite systems and at the limit of an infinite number of particles. We prove that the time-dependent densities per particle are given at the limit of an infinite number of particles by their respective mean-field quantities, and that the time-dependent reduced one-particle and two-particle density matrices per particle of the driven mixture are 100% condensed. Interestingly, the quasienergy per particle does not coincide with the mean-field value at this limit, unless the relative center-of-mass coordinate of the two Bose–Einstein condensates is not activated by the driving forces fL,1 and fL,2. As an application, we investigate the imprinting of angular momentum and its fluctuations when steering a Bose–Einstein condensate by an interacting bosonic impurity and the resulting modes of rotations. Whereas the expectation values per particle of the angular-momentum operator for the many-body and mean-field solutions coincide at the limit of an infinite number of particles, the respective fluctuations can differ substantially. The results are analyzed in terms of the transformation properties of the angular-momentum operator under translations and boosts, and as a function of the interactions between the particles. Implications are briefly discussed.

THE EFFECT OF 3dn IMPURITIES IN THE YBa2Cu3O7−δ SUPERCONDUCTOR

1993 ◽  
Vol 07 (22) ◽  
pp. 1449-1456
Author(s):  
G. A. R. LIMA ◽  
VITOR TORRES ◽  
A. FAZZIO
Keyword(s):  
Electronic Structure ◽  
Transition Metal ◽  
Atomic Number ◽  
Configuration Interaction ◽  
Narrow Band ◽  
Correlation Effects ◽  
Chemical Trends

The electronic structure of the CuO chain and the CuO 2 plane in the superconductor YBa 2 Cu 3 O 7−δ doped with 3dn transition-metal (TM) atoms are investigated. The calculations were performed through the semiempirical INDO/S technique, where the correlation effects are taken into account by the Configuration Interaction (CI) procedure. We also calculated, for all 3dn impurities, the Hubbard parameters Udd corresponding to a narrow band. The results obtained demonstrate clear chemical trends in the electronic structure of the 3d's, from Ti to Ni, when they substitute Cu(1) and Cu(2) sites; the hybridization decreases when the atomic number Z decreases. Our work provides a picture which is important to understand the change in T c when the host is doped with TM atom.

EFFECTS OF CORE POLARIZATION AND PAIRING CORRELATIONS ON SOME GROUND-STATE PROPERTIES OF DEFORMED ODD-MASS NUCLEI WITHIN THE HIGHER TAMM–DANCOFF APPROACH

2011 ◽  
Vol 20 (02) ◽  
pp. 252-258 ◽  
Author(s):  
LUDOVIC BONNEAU ◽  
JULIEN LE BLOAS ◽  
PHILIPPE QUENTIN ◽  
NIKOLAY MINKOV
Keyword(s):  
Ground State ◽  
Mean Field ◽  
Energy Difference ◽  
Pair Type ◽  
Many Body ◽  
Hartree Fock ◽  
Ground State Properties ◽  
Pairing Correlations ◽  
The Many ◽  
The Impact

In self-consistent mean-field approaches, the description of odd-mass nuclei requires to break the time-reversal invariance of the underlying one-body hamiltonian. This induces a polarization of the even-even core to which the odd nucleon is added. To properly describe the pairing correlations (in T = 1 and T = 0 channels) in such nuclei, we implement the particle-number conserving Higher Tamm–Dancoff approximation with a residual δ interaction in each isospin channel by restricting the many-body basis to two-particle–two–hole excitations of pair type (nn, pp and np) on top of the Hartree–Fock solution. We apply this approach to the calculation of two ground-state properties of well-deformed nuclei |Tz| = 1 nuclei around 24 Mg and 48 Cr , namely the isovector odd-even binding-energy difference and the magnetic dipole moment, focusing on the impact of pairing correlations.

scholarly journals Inverse mean field theories

2018 ◽  
Vol 20 (43) ◽  
pp. 27600-27610 ◽  
Author(s):  
Peter Schmitteckert
Keyword(s):  
Single Particle ◽  
Body Wave ◽  
Mean Field ◽  
Wave Functions ◽  
Field Theories ◽  
Many Body ◽  
Fermionic Systems ◽  
Mean Field Theories

In this work we discuss the extraction of mean field single particle Hamiltonians from many body wave functions of fermionic systems.

scholarly journals Neutrino-pair interactions in astrophysical systems

2020 ◽  
Vol 29 (09) ◽  
pp. 2050080
Author(s):  
María Paula Colombi ◽  
Osvaldo Civitarese ◽  
Ana V. Penacchioni
Keyword(s):  
Eigenvalue Problem ◽  
Body Problem ◽  
Mean Field ◽  
Response Functions ◽  
Many Body ◽  
Quasi Particle ◽  
Finite Density ◽  
Neutrino Pair ◽  
Neutrino Fluxes ◽  
Pair Interactions

We study the effects produced by interactions among neutrinos upon extra-galactic neutrino-fluxes. We have assumed a separable type of pair interactions and performed a transformation to a quasi-particle mean field followed by a Tamm–Damcoff diagonalization. In doing so, we have adopted techniques originated in the quantum many-body problem, and adapted them to this specific case. The solutions of the associated eigenvalue problem provide us with energies and amplitudes which are then used to construct the neutrino response functions at finite density and temperature. The formalism is applied to the description of neutrinos produced in a SN environment.

Elementary Principles

2018 ◽  
Author(s):  
Klaus Morawetz
Keyword(s):  
Large Deflection ◽  
Mean Field ◽  
Distribution Functions ◽  
Many Body ◽  
Many Body Theory ◽  
Binary Correlation ◽  
The Mean ◽  
The Many ◽  
Body Theory

The many-body theory combines ideas of thermodynamics with ideas of mechanics. In this introductory chapter, the symbiosis of these two different fields of physics is demonstrated on overly simplified models. We explore the principles of finite-range forces to show the twofold nature of virial corrections. Infrequent collisions with a large deflection angle lead to collision integrals and rather frequent encounters with deflections on small angles act as a mean field. The (mean-field) corrections to drift result in the internal pressure and the nonlocal correction to the collisions results in the effect of the molecular volumes. The concept of distribution functions is introduced and the measure of information as entropy. The binary correlation allows one to distinguish tails and cores of the interaction potential. The concept of binary correlation is thus behind the intuitive picture of the kinetic equation.

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