scholarly journals Angle-resolved study of density waves, superconductivity and pseudogap in two dimensions

2002 ◽  
Vol 12 (9) ◽  
pp. 65-68
Author(s):  
D. Zanchi
Keyword(s):  
Renormalization Group ◽  
Mean Field ◽  
Two Dimensions ◽  
Square Lattice ◽  
Correlated Electrons ◽  
Functional Renormalization Group ◽  
Half Filling ◽  
The Mean ◽  
Critical Scale ◽  
D Wave

Weakly correlated electrons on a square lattice are studied by angle-resolved functional renormalization group. Upon renormalization the interaction starts to depend on monienta and has pole-like solutions near the doping-dependent critical scale. Near half-filling this critical scale is the pseudogap temperature T*. In the overdoped regime the critical scale is the mean-field like critical temperature for d-wave superconductivity.

Some exact results from the mean field renormalization group

1992 ◽  
Vol 189 (1-2) ◽  
pp. 367-376 ◽  
Author(s):  
A. das Neves ◽  
J. Kamphorst Leal da Silva ◽  
J.A. Plascak
Keyword(s):  
Renormalization Group ◽  
Mean Field ◽  
Exact Results ◽  
The Mean ◽  
Field Renormalization

SUPERCONDUCTING CLASSES IN THE EXTENDED HUBBARD MODEL

1996 ◽  
Vol 10 (12) ◽  
pp. 1397-1423 ◽  
Author(s):  
MASA-AKI OZAKI ◽  
EIJI MIYAI ◽  
TOMOAKI KONISHI ◽  
KAORU HANAFUSA
Keyword(s):  
Hubbard Model ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
S Wave ◽  
Ferromagnetic Order ◽  
Numerical Studies ◽  
The Mean

This paper describes group theoretical classification of superconducting states (SC) in the extended Hubbard model with on-site repulsion (U), nearest neighbor attraction (V) and nearest neighbour exchange interaction (J) on the two-dimensional square lattice using the mean field approach. By decomposing the pairing interaction into irreducible parts; A1g, B1g and Eu of D4h point symmetry, we have derived two singlet SCs (s-wave and d-wave) from A1g and B1g, eight triplet SCs from Eu. The first three types of triplet SC have pairing by electrons with antiparallel spin, the second two types have pairing by electrons with equal spin and the last three types are non-unitary and have pairing by only up-spin electrons. We showed that three non-unitary states have to be accompanied with a ferromagnetic order from the structure of the maximal little groups. We performed numerical studies for these SCs. For parameters and electron density favorable for the ferromagnetic order, a non-unitary SC coexistent with ferromagnetism is most stable.

FLUCTUATION EFFECTS IN A CLASS OF SYSTEMS WITH TWO ORDER PARAMETERS

1993 ◽  
Vol 07 (27) ◽  
pp. 1725-1731 ◽  
Author(s):  
L. DE CESARE ◽  
I. RABUFFO ◽  
D.I. UZUNOV
Keyword(s):  
Phase Transition ◽  
Renormalization Group ◽  
Phase Transitions ◽  
Order Phase Transition ◽  
Mean Field ◽  
Ising Models ◽  
Order Parameters ◽  
The Mean ◽  
Fluctuation Effects ◽  
Second Order Phase Transition

The phase transitions described by coupled spin -1/2 Ising models are investigated with the help of the mean field and the renormalization group theories. Results for the type of possible phase transitions and their fluctuation properties are presented. A fluctuation-induced second-order phase transition is predicted.

ULTRASONIC ATTENUATION IN d-WAVE SUPERCONDUCTORS

2001 ◽  
Vol 15 (09n10) ◽  
pp. 269-276 ◽  
Author(s):  
TRIBIKRAM GUPTA ◽  
D. M. GAITONDE
Keyword(s):  
Dopant Concentration ◽  
Ultrasonic Attenuation ◽  
Mean Field Theory ◽  
Mean Field ◽  
Square Lattice ◽  
Clean Limit ◽  
Sign Change ◽  
Attenuation Rate ◽  
Interacting Electrons ◽  
D Wave

We consider a BCS-like model of interacting electrons on a square lattice. Within mean field theory, our model has an instability towards the formation of a d-wave superconducting state. We calculate the longitudinal ultrasonic attenuation rate in the superconducting phase in the clean limit for parameters appropriate to the cuprates. We find that the temperature dependence of the attenuation rate is similar to that observed in conventional superconductors for phonon wavevectors along the direction of the anti-nodes of the gap. However, the attenuation rate for phonon wavevectors along the nodal direction is found to be strikingly different in its temperature and doping dependence. The attenuation rate α S (T) increases in magnitude and shows a sign change in its curvature (when plotted as a function of temperature) with increasing value of dopant concentration.

scholarly journals ANTIFERROMAGNETISM, STRIPES, AND SUPERCONDUCTIVITY IN THE t–J MODEL WITH COULOMB INTERACTION

2001 ◽  
Vol 15 (08) ◽  
pp. 1117-1126 ◽  
Author(s):  
JUNGHOON HAN ◽  
QIANG-HUA WANG ◽  
DUNG-HAI LEE
Keyword(s):  
Long Range ◽  
Coulomb Interaction ◽  
Lower Energy ◽  
Mean Field ◽  
Doping Density ◽  
Stripe Width ◽  
The Mean ◽  
D Wave

We study mean-field phases of the t–J model with long-range Coulomb interaction. In the order of increasing doping density we find a classical antiferromagnet, charge and spin stripes, and a uniform d-wave superconductor, at the realistic doping parameters. Both in-phase and anti-phase stripes exist as metastable configurations, but the in-phase stripes have a slightly lower energy. The dependence of the stripe width and the inter-stripe spacing on the doping is examined. Effects of fluctuations around the mean-field states are discussed.

scholarly journals DYNAMICAL MODEL FOR VIRUS SPREAD

Fractals ◽  
1996 ◽  
Vol 04 (02) ◽  
pp. 113-122 ◽  
Author(s):  
G. CAMELO-NETO ◽  
S. COUTINHO
Keyword(s):  
Steady State ◽  
Mean Field ◽  
Field Approximation ◽  
Square Lattice ◽  
Mean Field Approximation ◽  
Model Parameters ◽  
Viral Spread ◽  
Infected Cells ◽  
The Mean ◽  
Density Population

The steady state properties of the mean density population of infected cells in a viral spread is simulated by a general forest like cellular automaton model with two distinct populations of cells (permissive and resistant ones) and studied in the framework of the mean field approximation. Stochastic dynamical ingredients are introduced into this model to mimic cells regeneration (with probability p) and to consider infection processes by other means than contiguity (with probability f). Simulations are carried out on a L×L square lattice taking into consideration the eighth first neighbors. The mean density population of infected cells (Di) is measured as a function of the regeneration probability p, and analyzed for small values of the ratio f/p and for distinct degrees of cell resistance. The results obtained by a mean field like approach recovers the simulations results. The role of the resistant parameter R (R≥2) on the steady state properties, is investigated and discussed in comparison with the R=1 monocell case which corresponds to the self organized critical forest model. The fractal dimension of the dead cells ulcers contours was also estimated and analyzed as a function of the model parameters.

scholarly journals Crystal fields induced compensation temperatures in a decorated square lattice

2021 ◽  
Author(s):  
HADEY MOHAMAD
Keyword(s):  
Mean Field Theory ◽  
Mean Field ◽  
Square Lattice ◽  
Present System ◽  
Long Range Order ◽  
Two Dimensional ◽  
Crystal Fields ◽  
Crystalline Anisotropy ◽  
The Mean ◽  
Magnetization Behavior

A two-sublattice decorated Blume-Capel ferrimagnet has been investigated using the mean field theory. Interesting behaviors of long-range order are obtained depending on particular magnitudes of magnetocrystalline anisotropies for both sublattices sites. Distinguishable features have been discovered in two-dimensional decorated lattice consisting of spin-5/2 and decorating spin-7/2 ions on the bonds. It is found the present system shows two ferrimagnetic compensation temperatures. However, one compensation temperature for different or fixed values of decorated magnetic anisotropies with the values of J1=-0.5 , J2=-1.0 , or with J1=-1.0 , J2=-0.5, has been induced, respectively. The magnetization behavior in the (M,DB/IJ2I) space has not already been considered showing the crystalline anisotropy dependence of total magnetization remanences. Besides, the variations of net magnetizations versus the decorated crystal fields, i.e., in the(M,DA/IJ2I) space, have been done, with J1=-0.5, J2=-1.0 , for various values of T=2.0, 2.5,3.0 , respectively.

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