scholarly journals Extended Hubbard model applied to study the pressure effects in high-temperature superconductors

1997 ◽  
Vol 56 (1) ◽  
pp. 466-469 ◽  
Author(s):  
E. V. L. de Mello ◽  
C. Acha
Keyword(s):  
High Temperature ◽  
Hubbard Model ◽  
High Temperature Superconductors ◽  
Pressure Effects ◽  
Extended Hubbard Model

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.

THE STUDY ON THE SPIN GAP PHENOMENON IN OXYGEN DEFICIENT YBa2Cu3O6+δ AND Ca-DOPED Y1-xCaxBa2Cu3O6+δ SUPERCONDUCTORS

1999 ◽  
Vol 13 (27) ◽  
pp. 3219-3234 ◽  
Author(s):  
L. J. SHEN ◽  
C. C. LAM ◽  
X. JIN ◽  
H. S. LAM ◽  
S. H. LI
Keyword(s):  
High Temperature ◽  
Normal State ◽  
High Temperature Superconductivity ◽  
Oxygen Deficiency ◽  
High Temperature Superconductors ◽  
Pressure Effects ◽  
Thermal Excitation ◽  
Metallic State ◽  
Specific Function ◽  
Spin Gap

The understanding of the spin gap phenomenon in the normal state of the high temperature superconductors can provide the mechanism of the high temperature superconductivity. A specific function of thermal excitation for quasiparticles was introduced based on the experimental relationship between resistivity and temperature. This specific function describes the deviation in resistivity from the T-linear relationship w.r.t. the normal state of the high temperature superconductors. With this function, the spin gap is naturally introduced. Our experimental results indicate that the spin gap behavior is closely related not only to the oxygen deficiency but also to the structural change in the a–b plane. Furthermore, we found that the crossover from anomalous metallic state to spin gap state takes place within a temperature range T S <T<T*, which depends on the oxygen content and the Ca-doping level. Pressure effects on the spin gap phenomenon in bulk samples of oxygen-deficient YBa 2 Cu 3 O 6+δ and Ca-doped Y 1-x Ca x Ba 2 Cu 3 O 6+δ were also investigated. Under high hydrostatic pressure the spin gap behavior is also severely influenced by the contraction of the a–b plane due to the pressure.

High-temperature series expansion for the extended Hubbard model

1995 ◽  
Vol 51 (20) ◽  
pp. 14077-14084 ◽  
Author(s):  
M. Bartkowiak ◽  
J. A. Henderson ◽  
J. Oitmaa ◽  
P. E. de Brito
Keyword(s):  
High Temperature ◽  
Hubbard Model ◽  
Series Expansion ◽  
Temperature Series ◽  
Extended Hubbard Model

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.

Pressure effects in high temperature superconductors

1994 ◽  
Vol 235-240 ◽  
pp. 2093-2094 ◽  
Author(s):  
M.Núñez Regueiro ◽  
M. Jaime ◽  
M.A.Alario Franco ◽  
J-J. Capponi ◽  
C. Chaillout ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Superconductors ◽  
Pressure Effects

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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