Thermodynamics of a Pseudospin-Electron Model Without Correlations

Stasyuk, I. V.; Shvaika, A. M.; Tabunshchyk, K. V.

doi:10.5488/cmp.2.1.109

Cited by 21 publications

(62 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…On the other hand, in the case of a fixed value of the field h the possibility of a uniform first-order phase transition (bistability) appears [7,9].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Dynamical susceptibilities in a strong coupling approach

Shvaika

2000

Physica C: Superconductivity

View full text Add to dashboard Cite

A general scheme to calculate dynamical susceptibilities of strongly correlated electron systems within the dynamical mean field theory is developed. The approach is based on an expansion over electron hopping around the atomic limit (within the diagrammatic technique for site operators: projection and Hubbard ones) in infinite dimensions. As an example, the Falicov-Kimball and simplified pseudospin-electron models are considered and analytical expressions for the dynamical susceptibilities are obtained.In the last decade the main achievements in the theory of the strongly correlated electron systems are connected with the development of the Dynamical Mean Field Theory (DMFT) which is exact in the d = ∞ limit [1]. It was shown by Metzner and Vollhardt [2,3] that in the d = ∞ limit self-energies are single-site quantities (do not depend on wave vector) which leads to a significant simplification. The same is true for the four-vertices in the Bethe-Salpeter equation for susceptibilities (see [1]).The aim of this article is to develop a general scheme to calculate dynamical susceptibilities within a diagrammatic technique for site operators (projection or Hubbard ones) for strongly correlated electron systems described by the general statistical operatorT expis a sum of the single-site contributions. Our approach is based on an expansion over electron hopping around the atomic limit [3] (see also [4]) instead of an expansion in the local interaction [1].In the d = ∞ limit, the lattice problem with tis mapped onto an effective atomic problem with a dynamical mean field tmined by the same single-site irreducible parts Ξ σ (ω ν ) [3] and a closed set of equations for Ξ σ (ω ν ) and J σ (ω ν ) can be written [1]. Here, irreducible parts are contributions to the single-site Green's function which cannot be divided into parts by cutting one hopping line. In a similar way, the expansion for correlation functions built on operatorsÂ andB in terms of the hopping iswhere thin wavy lines denote electron hopping integrals t σ ij (τ − τ ′ ) and arrows denote singleparticle Green's functions. In eq. (2), , and L are single-site quantities, which are the same for the lattice and the effective atomic problems and are generalized many-particle Green's functions [4] which will be calculated within DMFT.To do this, we calculate a two-particle Green's function for the effective atomic problem , which, on the other hand, can be written in the following way:

show abstract

“…On the other hand, in the case of a fixed value of the field h the possibility of a uniform first-order phase transition (bistability) appears [7,9].…”

mentioning

confidence: 99%

“…The single-particle Green's function for the effective atomic problem is a coherent sum of the Green's functions for subspaces S z i = ± 1 2 and is equal to [6,7] …”

mentioning

confidence: 99%

Dynamical susceptibilities in a strong coupling approach

Shvaika

2000

Physica C: Superconductivity

View full text Add to dashboard Cite

show abstract

“…The investigations of the PEM revealed a possibility of phase transition to chess-board phase as well as incommensurate phase, the transition between uniform phases, the transition to a superconducting state, the existence of phase separation region and other peculiarities [15][16][17][18][19][20]. Let us introduce a single-site basis of states:…”

Section: Pem With Strong Interactionmentioning

confidence: 99%

Raman Light Scattering in Pseudospin-Electron Model at Strong Pseudospin-Electron Interaction

Mysakovych¹,

Stasyuk²

2004

Condens. Matter Phys.

View full text Add to dashboard Cite

Anharmonic phonon contributions to Raman scattering in locally anharmonic crystal systems in the framework of the pseudospin-electron model with tunneling splitting of levels are investigated. The case of strong pseudospin-electron coupling is considered. Pseudospin and electron contributions to scattering are taken into account. Frequency dependences of Raman scattering intensity for different values of model parameters and for different polarization of scattering and incident light are investigated.

show abstract

“…The main difference between these models lies in the way how an averaging procedure is performed (thermal statistical averaging in the case of PEM and Falicov-Kimball model, configurational averaging for binary alloy) [3,4]. This Hamiltonian is also invariant with respect to the transformation µ → −µ, h → 2g − h, n → 2−n, S z → −S z .…”

Section: Introductionmentioning

confidence: 99%

“…In the previous papers [5][6][7], a self-consistent scheme was proposed for the calculation of mean values of pseudospin and electron number operators, grand canonical potential as well as correlation functions of simplified PEM. The main idea of the approach was based on the GRPA scheme [8] with the inclusion of the mean field type contributions coming from the effective pseudospin interactions via conducting electrons [5].…”

Section: Introductionmentioning

confidence: 99%

Pseudospin-Electron Model in the Self-Consistent Gaussian Fluctuation Approximation

Stasyuk¹,

Tabunshchyk²

2001

Condens. Matter Phys.

View full text Add to dashboard Cite

Pseudospin-electron model with an effective many-body interaction between pseudospins via conducting electrons is investigated within the generalized random phase approximation scheme with the self-consistent inclusion of mean field type contributions (coming from the effective pseudospin interaction) as well as gaussian fluctuations of the mean field (which makes it possible to obtain more accurate results in the vicinity of the critical points). Using the approach proposed here, the expressions are obtained for the pseudospin correlation function, for pseudospin mean value, as well as for the grand canonical potential.

show abstract

Thermodynamics of a Pseudospin-Electron Model Without Correlations

Cited by 21 publications

References 16 publications

Dynamical susceptibilities in a strong coupling approach

Dynamical susceptibilities in a strong coupling approach

Raman Light Scattering in Pseudospin-Electron Model at Strong Pseudospin-Electron Interaction

Pseudospin-Electron Model in the Self-Consistent Gaussian Fluctuation Approximation

Contact Info

Product

Resources

About