Thermodynamics of Pseudospin-Electron Model in Mean Field Approximation

The static and dynamic dielectric susceptibility of the pseudospin-electron model is investigated in the random phase approximation. The possibility of the phase transition to the homogeneous phase, to the phase with doubly modulated lattice period and to the incommensurate phase is revealed in the regime µ = const depending on the value of the chemical potential. The phase separation on the homogeneous and phase with doubly modulated lattice period is established and the phase diagrams (n, h) are built. The influence of the tunnelling-like splitting on the phase transition picture is studied. The presence of pseudospin-wave excitations and the smooth excitation spectrum and the possibility of their superimposing are revealed.

Section: Introductionsupporting

confidence: 83%

Pseudospin-Electron Model at Weak Coupling

Stasyuk¹,

Mysakovych²

2002

“…Such inclusions lead to the renormalization of energies of the electron levels [23]. In particular, at…”

Section: Static Mean-field Approximation (mentioning

confidence: 99%

Approximate Analytical Dynamical Mean-Field Approach to Strongly Correlated Electron Systems

Stasyuk¹

2000

An approximate analytical scheme of the dynamical mean-field theory (DMFT), that is used for electron systems with Hubbard correlations and is exact in the limit of the infinite dimensionality of a space, is developed. The effective single-site problem arising in the framework of this method is formulated in terms of the auxiliary Fermi-field. The irreducible Green's function technique with the projecting on the Hubbard basis of Fermi-operators is used for its solution. A system of DMFT equations is obtained in the approximation which is a generalization of the Hubbard-III approximation and combines it with a self-consistent renormalization of the local electron levels. It is shown that the proposed approach includes as simple specific cases a number of known approximations (Hubbard-III, AA, MAA, . . . ) based on the assumption of the single-site structure of the electron selfenergy.

“…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%

“…For a self-consistency, such a renormalization should be also done in the expressions for Fermi-type Green functions G pq [17]. In our numerical calculations we do not take into account this renormalization.…”

Section: Correlators In Grpamentioning

confidence: 99%

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

Mysakovych¹,

Stasyuk²

2004

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.