Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 x 2 cluster

Тип публикации: статья из журнала

Год издания: 2010

Идентификатор DOI: 10.1134/S1063776110100146

Ключевые слова: Antiferromagnetic orders, Characteristic energy, Cluster perturbation theories, Coulomb repulsions, Density of state, Dynamic mean field theories, Eigenvalue problem, Exact diagonalization, Excited levels, Finite temperatures, Half-filling, Hubbard, Metal insulator transition temperature, Nearest neighbors, Numerical solution, Pseudo-gap, Quasiparticle spectrum, Shadow zone, Short-range magnetic orders, Temperature evolution, Zero temperatures, Antiferromagnetism, Eigenvalues and eigenfunctions, Fermi level, Hubbard model, Mean field theory, Metal insulator boundaries, Perturbation techniques, Semiconductor insulator boundaries, Statistical mechanics, Metal insulator transition

Аннотация: The cluster perturbation theory is presented in the 2D Hubbard model constructed using X operators in the Hubbard-I approximation. The short-range magnetic order is taken into account by dividing the entire lattice into individual 2 x 2 clusters and solving the eigenvalue problem in an individual cluster using exact diagonalization taking into account all excited levels. The case of half-filling taking into account jumps between nearest neighbors is considered. As a result of numerical solution, a shadow zone is discovered in the quasiparticle spectrum. It is also found that a gap in the density of states in the quasiparticle spectrum at zero temperature exists for indefinitely small values of Coulomb repulsion parameter U and increases with this parameter. It is found that the presence of this gap in the spectrum is due to the formation of a short-range antiferromagnetic order. An analysis of the temperature evolution of the density of states shows that the metal-insulator transition occurs continuously. The existence of two characteristic energy scales at finite temperatures is demonstrated, the larger scale is associated with the formation of a pseudogap in the vicinity of the Fermi level, and the smaller scale is associated with the metal-insulator transition temperature. A peak in the density of states at the Fermi level, which is predicted in the dynamic mean field theory in the vicinity of the metal-insulator transition, is not observed.

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Издание

Журнал: JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS

Выпуск журнала: Vol. 111, Is. 4

Номера страниц: 635-644

ISSN журнала: 10637761

Место издания: NEW YORK

Издатель: MAIK NAUKA/INTERPERIODICA/SPRINGER

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