Introduction

Берсукер, И. Б.; Polinger, V. Z.

doi:10.1007/978-3-642-83479-0_1

Cited by 50 publications

(131 citation statements)

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“…In the closely related E ⊗ e JT effect [12][13][14], a similar Mathieu's equation arises, but with three-fold degeneracy (corresponding to elongation of the octahedron along an x, y, or z axis). This problem is often simplified by approximating the intercell coupling by a quadratic form.…”

Section: B Intracell Hamiltonian: Static Jt Effectmentioning

confidence: 99%

“…This seems to be the case in the cuprates: the octahedral strain in the LTO phase is found to be a secondary order parameter, proportional to the square of the octahedral tilt angle [24]. These strains may be formally decoupled from the problem, following standard practice [12][13][14], by defining…”

Section: Eliminating the Strain And Acoustic Phonon Modesmentioning

confidence: 99%

“…A similar effect can arise in a solid, either for a local impurity or for a collective JT effect in the crystal as a whole. Many perovskites and related structures have a phase transition to either a ferroelectric or antiferrodistortive phase, which can be interpreted as a collective JT effect [13].…”

Section: First-order Band Jt Effectmentioning

confidence: 99%

“…16. Alternatively, a pseudospin formalism [12][13][14]29] (Appendix IV) can be employed. In the two-dimensional subspace spanned by the electronic operators a † 1 ( l), a † 2 ( l), the ρ operators can be represented by Pauli matrices…”

Section: B Intracell Hamiltonian: Static Jt Effectmentioning

confidence: 99%

“…I have recently suggested [10,11] that both LTT and LTO phases are manifestations of a novel form of band Jahn-Teller (JT) effect [12][13][14], in which the degenerate electronic states are associated with the two vHs's. Thus, the LTT phase involves an essentially static band JT distortion, splitting the degeneracy of the two vHs's.…”

Section: Introductionmentioning

confidence: 99%

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Van Hove excitons and high-Tc superconductivity

Markiewicz

1993

Physica C: Superconductivity

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The possible role of the van Hove singularity (vHs) in stabilizing the low-temperature orthorhombic (LTO) phase transition in La 2−x Sr x CuO 4 (LSCO) is discussed. It is found that the vHs can drive a structural distortion in two different ways, either due to spin-orbit coupling or to dynamic Jahn-Teller (JT) effects. This paper discusses the latter effect in some detail. It is shown that a model Hamiltonian introduced earlier to describe the coupled electron -octahedral tilt motions ('cageons') has a series of phase transitions, from a high-temperature disordered JT phase (similar to the high-temperature tetragonal phase of LSCO) to an intermediate temperature dynamic JT phase, of average orthorhombic symmetry (the LTO phase) to a low temperature static JT phase (the low temperature tetragonal phase). For some parameter values, the static JT phase is absent.

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Section: B Intracell Hamiltonian: Static Jt Effectmentioning

confidence: 99%

Section: Eliminating the Strain And Acoustic Phonon Modesmentioning

confidence: 99%

Section: First-order Band Jt Effectmentioning

confidence: 99%

Section: B Intracell Hamiltonian: Static Jt Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Van Hove excitons and high-Tc superconductivity

Markiewicz

1993

Physica C: Superconductivity

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Limitations of density functional theory in application to degenerate states

Берсукер

1997

J. Comput. Chem.

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It is shown that the claims that density functional theory (DFT) can handle orbitally degenerate states are ungrounded. The constraint search formulation of DFT allows one to determine a set of densities and eigenvalues for the degenerate term that, however, are neither observables, nor can they be used to solve the system of coupled equations for the nuclear motions to obtain observables, as in the wave function presentation. A striking example of the failure of the existing versions of DFT to describe degenerate states is provided by the Berry phase problem: the strong dependence of the results on the phase properties of the electronic wave function that are smeared out in the density formulation. The solution of the Jahn‐Teller E‐e problem illustrates these statements. For nondegenerate states with the full wave function taken in the adiabatic approximation as a product of the electronic and nuclear parts, the formulation of DFT is rigorous if and only if the dependence of the electronic wave function on nuclear coordinates is ignored. This lowers the accuracy of the results, in general, and may lead to erroneous presentation as in the case of molecular systems in strong magnetic fields. © 1997 by John Wiley & Sons, Inc.

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Pseudo-Jahn-Teller Centers and Local Structure of Doped Cuprates

Moskvin

Panov

1999

phys. stat. sol. (b)

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Introduction

Cited by 50 publications

References 13 publications

Van Hove excitons and high-Tc superconductivity

Van Hove excitons and high-Tc superconductivity

Limitations of density functional theory in application to degenerate states

Pseudo-Jahn-Teller Centers and Local Structure of Doped Cuprates

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