Study of correlation functions in molecular crystals

1989 ◽  
Vol 67 (11) ◽  
pp. 1036-1039
Author(s):  
M. S. Wartak ◽  
C. Y. Fong
Keyword(s):  
Correlation Function ◽  
High Temperature ◽  
Hubbard Model ◽  
Correlation Functions ◽  
Nearest Neighbor ◽  
High Temperature Superconductors ◽  
Molecular Crystals ◽  
Vibrational Properties ◽  
Model Hamiltonian

We have studied the correlation functions for a model Hamiltonian describing the vibrational properties in molecular crystals. The model Hamiltonian consists of terms characterizing the on-site anharmonicity and the nearest-neighbor hopping interaction. If the on-site anharmonicity is uniform, the correlation functions exhibit no structure. However, structure appears in the nearest-neighbor correlation function if the anharmonicity is nonuniform. Because the Hamiltonian resembles the Hubbard model for the electronic case, the implication of the results to high temperature superconductors is indicated.

TWO-DIMENSIONAL QUARTER-FILLED EXTENDED HUBBARD MODEL AT STRONG COUPLING

2005 ◽  
Vol 19 (01n03) ◽  
pp. 213-216
Author(s):  
W. F. LEE ◽  
H. Q. LIN
Keyword(s):  
Hubbard Model ◽  
Correlation Functions ◽  
Nearest Neighbor ◽  
Spin Correlation ◽  
Perturbation Approach ◽  
Effective Hamiltonian ◽  
Two Dimensional ◽  
Extended Hubbard Model ◽  
Neighbor Interaction ◽  
Electron Hopping

In this paper, we generalized the perturbation approach to study the quasi-two-dimension extended Hubbard model. This model is characterizing by intra-chain electron hopping t, on-site Column interaction U, nearest-neighbor interaction V, and inter-chain electron hopping t′ and nearest-neighbor interaction V′. An effective Hamiltonian up to sixth-order in t/U, t/V, t/V′, t′/U, t′/V and t′/V′ expansion was obtained and the spin-spin correlation functions were calculated. We presented results for t=t′, V=V′.

Application of the SD Technique for Solving a BCS-Reduced Hubbard like Hamiltonian

1997 ◽  
Vol 08 (05) ◽  
pp. 1037-1061 ◽  
Author(s):  
Werner Fettes ◽  
Ingo Morgenstern ◽  
Thomas Husslein
Keyword(s):  
Physical Properties ◽  
Hubbard Model ◽  
Detailed Analysis ◽  
Ground State ◽  
Correlation Functions ◽  
Nearest Neighbor ◽  
Exact Diagonalization ◽  
Long Range Order ◽  
Technical Details ◽  
Diagonalization Algorithm

We present exact and stochastic diagonalization results for a BCS-reduced Hubbard model. The kinetic Hamiltonian is the same as in the single band Hubbard model with additional next nearest neighbor hopping. The interaction of this model is designed to inhibit superconductivity in the d x2-y2 channel. The ground state of this model is studied by exact and stochastic diagonalization technique. We present a review of the technical details of the application of the stochastic diagonalization algorithm on this problem. To verify our results obtained with the stochastic diagonalization, they are compared with the exact diagonalization results. In order to show the convergence of the stochastic diagonalization we give a detailed analysis of the behavior of physical properties with increasing number of states. Finally we study superconductivity in this BCS-reduced Hubbard model. As an indicator of superconductivity we use the occurrence of Off Diagonal Long Range Order. We study the scaling behavior of this model for various attractive interactions and in addition the dependence of the superconducting correlation functions from the filling of the system.

scholarly journals Stripe order enhanced superconductivity in the Hubbard model

2021 ◽  
Vol 119 (1) ◽  
pp. e2109406119
Author(s):  
Hong-Chen Jiang ◽  
Steven A. Kivelson
Keyword(s):  
High Temperature ◽  
Hubbard Model ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Long Distance ◽  
Positive Role ◽  
Density Matrix Renormalization ◽  
Period 2 ◽  
Stripe Order

Unidirectional (“stripe”) charge density wave order has now been established as a ubiquitous feature in the phase diagram of the cuprate high-temperature superconductors, where it generally competes with superconductivity. Nonetheless, on theoretical grounds it has been conjectured that stripe order (or other forms of “optimal” inhomogeneity) may play an essential positive role in the mechanism of high-temperature superconductivity. Here, we report density matrix renormalization group studies of the Hubbard model on long four- and six-leg cylinders, where the hopping matrix elements transverse to the long direction are periodically modulated—mimicking the effect of putative period 2 stripe order. We find that even modest amplitude modulations can enhance the long-distance superconducting correlations by many orders of magnitude and drive the system into a phase with a substantial spin gap and superconducting quasi–long-range order with a Luttinger exponent, Ksc∼1.

scholarly journals GLASS MODEL, HUBBARD MODEL AND HIGH-TEMPERATURE SUPERCONDUCTIVITY

1999 ◽  
Vol 10 (01) ◽  
pp. 309-320 ◽  
Author(s):  
INGO MORGENSTERN ◽  
WERNER FETTES ◽  
THOMAS HUSSLEIN ◽  
DENNIS M. NEWNS ◽  
PRATAP C. PATTNAIK
Keyword(s):  
High Temperature ◽  
Hubbard Model ◽  
High Temperature Superconductivity ◽  
High Temperature Superconductors ◽  
Finite Size ◽  
Microscopic Level ◽  
Finite Size Scaling ◽  
Microscopic Mechanism ◽  
Glass Model ◽  
Superconducting Correlations

In this paper we revisit the glass model describing the macroscopic behavior of the High-Temperature superconductors. We link the glass model at the microscopic level to the striped phase phenomenon, recently discussed widely. The size of the striped phase domains is consistent with earlier predictions of the glass model when it was introduced for High-Temperature Superconductivity in 1987. In an additional step we use the Hubbard model to describe the microscopic mechanism for d-wave pairing within these finite size stripes. We discuss the implications for superconducting correlations of the Hubbard model, which are much higher for stripes than for squares, for finite size scaling, and for the new view of the glass model picture.

QUASIPARTICLES IN HIGH-TEMPERATURE SUPERCONDUCTORS

2003 ◽  
Vol 17 (04n06) ◽  
pp. 578-583
Author(s):  
ROBERTA CITRO ◽  
MARIA MARINARO ◽  
K. NAKAGAWA
Keyword(s):  
High Temperature ◽  
Energy Distribution ◽  
Hubbard Model ◽  
Spectral Function ◽  
Momentum Distribution ◽  
Distribution Curve ◽  
High Temperature Superconductors ◽  
Quantum Criticality ◽  
Energy Distribution Curve ◽  
Coupling Approach

We study the quantum criticality effects induced by a singular charge vertex on the quasiparticle spectral function of an extended single-band Hubbard model. It is shown that the spectral intensity computed in a strong-coupling approach, reproduces the Momentum Distribution Curve (MDC) and the Energy Distribution Curve (EDC) of ARPES experiments on Bi 2 Sr 2 CaCu 2 O 8+δ.

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