Emery model

One of the simple models of high-Tc superconducting copper oxides is a two-band Hubbard Hamiltonian (so called Emery model) [46] 

The Hamiltonian (58) commutes with the operator that displaces all the spins by one unit cell cyclically. Therefore, the eigenfunctions of (58) must be characterized by hole quasi-impulse k = 2nmlN (m=l,2...N). The symmetry adapted basis functions corresponding to a fixed value of k can be constructed by the usual group theory technique. 

Omitting simple manipulations with the cyclic permutations, we can rewrite the Hamiltonian (1) in the following form  

to use the spin permutation technique we constructed the symmetry adapted lattice Hamiltonian in a compact operator form and essentially reduced the dimensionality of the corresponding eigenvalue problem. The effects of tpp 0 and the additional superexchange of copper holes are considered in [48]. 

Many body VB ansatze. From polymers and ladder materials to the square lattice 

---

OXYGEN-RELATED BAND-FEATURES OF THE EXTENDED EMERY MODEL FOR THE HTS CUPRATES... 

In this paper, we show that the observed band-properties can be described within the CT limit of the Emery model, taking into account, beyond the perturbation level, the direct oxygen-oxygen overlap t, treated by the infinite U paramagnetic slave boson method. 

Oxygen-Related Band-Features of theExtended Emery Model for the HTS 141... 

Anderson s lattice-like limit of the Emery model... 

To relate the above results to the physical systems, we now give the comparison of the calculated band structure in the Anderson lattice-like limit of the Emery model with the ARPES data on LSCO [6]. The regime of the bare parameters is Ap[Pg.142]

The observed evolution of the shape of the band-structure upon doping satisfies the Luttinger sum rule [9], It should be noted that only in the Anderson lattice-like limit of the Emery model it is possible to obtain the observed evolution of the FS upon doping. In all other cases, the oxygen symmetry of the FS can be attributed to the (non-renormalized) oxygen band and therefore the strong doping dependence of the band structure cannot be expected. 

Another model based on Emery and Drickamer s theory (Schimpf and Semenov, 2004) yields... 

Hopfinger, A.J., Compadre, R.L.L., Koehler, M.G., Emery, S. and Seydel, J.K. (1987). An Extended QSAR Analysis of Some 4-Aminodiphenylsulfone Antibacterial Agents Using Molecular Modeling and LFE-Relationships. Quant. Struct.-ActRelat, 6,111-117. 

The Blume-Emery-Griffiths (BEG) model is one of the well-known spin lattice models in equilibrium statistical mechanics. It was originally introduced with the aim to account for phase separation in helium mixtures [30]. Besides various thermodynamic properties, the model has been extended to study the structural phase transitions in many bulk systems. By... 

Blume M, Emery VJ, Griffiths RB. Ising model for the A transition and phase separation in He3-He4 mixtures. Physical Review A. 1971 4 1071-1077. DOI 10.1103/Phys-RevA.4.1071. 

Berker AN, Wortis M. Blume-Emery-Griffiths-Potts model in two dimensions phase diagram and critical properties from a position-space renormalization group. Physical Review B. 1976 14 4946-4963. DOI 10.1103/PhysRevB.14.4946. 

Hoston W, Berker AN. Multicritical phase diagrams of the Blume-Emery-Griffiths model with repulsive biquadratic coupling. Physical Review Letters. 1991 67 1027-1030. DOI 10.1103/PhysRevLett.67.1027. 

Yj for spin-flip. The model is that of Luther and Emery [lj, before they introduce new quasi-fermion operators to obtain a gap at Yll — - 3/s. The free energy corresponding to... 

These unusual pseudobinary phase diagrams were derived initially by Meijering (1950) from a simple mixture model for ternary mixtures. Much later, Blume, Emery and Griffiths (1971) deduced the same diagrams from a three-spin model of helium mixtures. The third diagram on the right of figure A2.5.30 is essentially that found experimentally for the fluid mixture He+ He the dashed line (second-order transition) is that of the A,-transition. 

This Blume-Emery-Griffiths (BEG) model [74] has been studied both by mean field calculations as well as by simulations. There is no pronounced difference between the amphiphile molecules 5 = 0, the oil or the water. Indeed, the model was first suggested in a quite different context. An extension of the model by Schick and Shih [75] includes an additional interaction of the form... 

Emery, F. (1993), The Nine-Step Model, in The Social Engagement of Social Science A Tavistock Anthology, E. Trist and H. Murray, Eds., University of Pennsylvania Press, Philadelphia. 

---