IMPURITY STATES IN SUPERCONDUCTING SYSTEMS WITH STRIPE LIKE MODULATION

2005 ◽  
Vol 19 (01n03) ◽  
pp. 267-269
Author(s):  
TIANLONG XIA ◽  
QIANG HAN ◽  
YAN CHEN ◽  
Z. D. WANG ◽  
X.-G. LI
Keyword(s):  
Nearest Neighbor ◽  
Local Density ◽  
Mean Field ◽  
Potential Scattering ◽  
Local Density Of States ◽  
Impurity States ◽  
Stripe Phase ◽  
Significant Difference ◽  
Underdoped Region ◽  
The Mean

Based on the extended Hubbard model with the next nearest neighbor hopping term, we study the impurity states in a slightly underdoped (with 0.13 hole) system with competition between d-wave superconductivity and antiferromagnetism by solving the mean field Bogoliubov-de Gennes equations self-consistently. Nickel and Zinc impurities are studied respectively using the potential scattering impurity (PSI) model and the Anderson impurity (AI) model. The significant difference in their local density of states may be useful to predict the impurity states in the stripe phase of the superconductors in the slightly underdoped region.

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.

Re-Examination of A1 → L10 Ordering: Generalized Bragg-Williams Model with Elastic Relaxation

2011 ◽  
Vol 172-174 ◽  
pp. 608-617 ◽  
Author(s):  
William A. Soffa ◽  
David E. Laughlin ◽  
Nitin Singh
Keyword(s):  
Nearest Neighbor ◽  
Binary Solution ◽  
Mean Field ◽  
Lattice Relaxation ◽  
Two Phase ◽  
First Order ◽  
Tetragonal Lattice ◽  
Wide Range ◽  
Third Law Of Thermodynamics ◽  
The Mean

The tetragonal lattice relaxation has been included in the thermodynamics of the fcc→L10ordering to produce a first-order character of the transition within the mean field description of the binary solution energetics. In view of growing interest in such systems e.g. Fe-Pd and Co-Pt alloys, which display a wide range of applications relevant to current and futuristic technologies, the fcc→L10two-phase field is re-examined utilizing a generalized Bragg-Williams approach including first and second nearest neighbor interactions. The thermodynamic behavior is examined in the limit of T→0K and discussed in terms of the implications of the Third Law of Thermodynamics.

Automated Functional Color Field Tester (FCFTester) Trends and Reproducibility – A Multicenter Pilot Study

2021 ◽  
pp. 293-301
Keyword(s):  
Pilot Study ◽  
Visual Field ◽  
Mean Field ◽  
Field Testing ◽  
Field Size ◽  
Exclusion Criteria ◽  
Significant Difference ◽  
The Mean ◽  
Color Field ◽  
Present Pilot Study

Background: The present study was designed to assess a protocol for investigating normative trends of kinetic color visual field sizes and reproducibility of such utilizing the Automated Functional Color Field Tester (FCFTester). Methods: The participants were recruited at three clinical sites. The participants were screened for the study based on a questionnaire designed by the authors to help assess the inclusion and exclusion criteria. There were 116 adult-only participants, however, only those reporting White race (n = 106) were used for statistical analysis. The mean age was 35.8 (std = 14) and nearly 70% of the sample was female. Results: This study demonstrated that kinetic visual field sizes across all four color isopters are not influenced by gender (p = 0.96) nor eye tested (p = 0.46). Only a slight difference in mean visual field sizes was found between the three clinical sites ranging from less than 2.5 degrees when the target was blue or green to less than 1.5 degrees for white or red targets. Overall, age had limited, yet significant, influence on kinetic field sizes likely related to the relatively young age of our participants. A significant difference in mean field size existed when comparing the four color isopters with an ascending order of green, red, blue, and white. This pattern was consistent across the three testing sites. Variability in field size for each color isopter was slight across the three clinical sites. Conclusion: The present pilot study shows promise that a protocol can be established to provide reproducible data and normative trends in kinetic color visual field testing. The authors recognize that this should be achievable with further refinement of the current testing protocol.

The Glauber and Metropolis Transition Rates on the Stationary States of the Ising Model

1997 ◽  
Vol 11 (13) ◽  
pp. 565-570
Author(s):  
G. L. S. Paula ◽  
W. Figueiredo
Keyword(s):  
Ising Model ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Field Approximation ◽  
Two Dimensions ◽  
Mean Field Approximation ◽  
Stationary States ◽  
Transition Rates ◽  
The Mean ◽  
The One

We have applied the Glauber and Metropolis prescriptions to investigate the stationary states of the Ising model in one and two dimensions. We have employed the formalism of the master equation to follow the evolution of the system towards the stationary states. Although the Glauber and Metropolis transition rates lead the system to the same equilibrium states for the Ising model in the Monte Carlo simulations, we show that they can predict different results if we disregard the correlations between spins. The critical temperature of the one-dimensional Ising model cannot even be found by using the Metropolis algorithm and the mean field approximation. However, taking into account only correlations between nearest neighbor spins, the resulting stationary states become identical for both Glauber and Metropolis transition rates.

scholarly journals On the Nearest-Neighbor Algorithm for the Mean-Field Traveling Salesman Problem

2014 ◽  
Vol 51 (01) ◽  
pp. 106-117
Author(s):  
Antar Bandyopadhyay ◽  
Farkhondeh Sajadi
Keyword(s):  
Approximation Algorithm ◽  
Traveling Salesman Problem ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Traveling Salesman ◽  
Nearest Neighbor Algorithm ◽  
Scaling Properties ◽  
Limiting Behavior ◽  
Total Length ◽  
The Mean

In this work we consider the mean-field traveling salesman problem, where the intercity distances are taken to be independent and identically distributed with some distribution F. We consider the simplest approximation algorithm, namely, the nearest-neighbor algorithm, where the rule is to move to the nearest nonvisited city. We show that the limiting behavior of the total length of the nearest-neighbor tour depends on the scaling properties of the density of F at 0 and derive the limits for all possible cases of general F.

A Cluster Calculation of B and P Impurities in Amorphous Silicon

1990 ◽  
Vol 209 ◽  
Author(s):  
L. Enrique Sansores ◽  
R.M. Valladares ◽  
J.A. Cogordan ◽  
A.A. Valladares
Keyword(s):  
Solid State ◽  
Density Of States ◽  
Nearest Neighbor ◽  
Local Density ◽  
Cluster Calculation ◽  
Local Density Of States ◽  
Ionic Component ◽  
Pure Silicon ◽  
Hartree Fock ◽  
Covalent Nature

ABSTRACTThe local density of states and charge density contours of clusters of the type ISi20H28, where I can be Si, B or P, was calculated using the well-known pseudopotential SCF Hartree-Fock Method (and the HONDO Program). It is found that the covalent nature of the bonding in pure silicon gets altered and gives rise to an ionic component when B and P are substituted in the center of the cluster. Also, the local density of states in the neighborhood of a Si atom, nearest neighbor to the center of the cluster, show a splitting of the p-states at the top of the valence band in pure silicon when B is substituted, and a new p-state appears in the band gap when P is sustituted. These results are analyzed in the light of the local changes and its relevance to the solid state properties.

Modulated Phases on the FCC(110) Surfaces with Adsorbate-Induced Reconstructions

2003 ◽  
Vol 10 (02n03) ◽  
pp. 189-194
Author(s):  
Min Kang ◽  
Makoto Kaburagi
Keyword(s):  
Phase Diagram ◽  
Monte Carlo ◽  
Correlation Function ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Modulated Phases ◽  
The Mean ◽  
Beg Model

We theoretically investigate the fcc(110) surfaces with missing row reconstructions induced by adatoms using the Blume–Emmery–Griffith (BEG) model. In the model, Kij is introduced to denote interactions between surface atoms and Jij to describe interactions between dipoles. The investigation by the mean field approximation has predicted that there appear modulated phases on the surfaces as the next-nearest-neighbor (NNN) and the nearest-neighbor (NN) interactions along the [001] direction become competitive. In this study, Monte Carlo simulations are performed to confirm the prediction. A correlation function defined by concentration operators in wave vector q space is calculated. The results show that the concentration modulations appear. The temperature versus the ratio of the NNN interaction K2 to the NN interaction K1 phase diagram is obtained. The possible features of the modulated phases in experiments are discussed.

MEAN FIELD APPROACH TO THE GAP OF A MODEL INTERACTING SYSTEM

1988 ◽  
Vol 02 (01) ◽  
pp. 87-101
Author(s):  
KAJOLI BANERJEE ◽  
VIJAY A. SINGH ◽  
G. R. BHAT
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Mean Field ◽  
Functional Theory ◽  
One Dimensional ◽  
Coulomb Term ◽  
The Density Functional Theory ◽  
The Mean ◽  
Transfer Term ◽  
Mean Field Approximations

The well-known local density approximation severely underestimates the gap of insulating materials. We undertake a study of an infinite one-dimensional model interacting system where the gap is known exactly. We use variational procedures, similar in spirit to Hohenberg and Kohn's derivation of the density functional theory. The mean field approximations so obtained are used to calculate the gap in the eigenspectrum. The gap is found to be systematically underestimated for realistic values of the parameters (u/t ≤ 4 where u is the Coulomb term and t, the transfer term). For u/t > 4, the approximate gap is in close agreement with the exact gap. The underestimation of the gap is investigated with respect to the discontinuity in the effective potential.

scholarly journals Phase Diagram of the Attractive Kane-Mele-Hubbard Model at Half Filling

Atoms ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 58
Author(s):  
Zlatko Koinov
Keyword(s):  
Phase Diagram ◽  
Optical Lattices ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Recent Developments ◽  
Topological States ◽  
Half Filling ◽  
The Mean

Motivated by recent developments in the experimental study of ultracold atoms in graphene-like honeycomb optical lattices, we investigate superconductivity of the attractive Kane-Mele-Habbard (KMH) model with the next-nearest-neighbor (NNN) hoping at half filling. The mean-field approximation is used to study the phase diagram which interpolates the trivial and the non-trivial topological states. It is shown that: (a) when the NNN hoping is taken into account, one has to introduce two mean-field gap equations for the two sublattices, instead of a single gap when the NNN hopping is neglected, and (b) in the non-trivial topological region the phase diagram with the NNN hopping is significantly different compared to the phase diagram calculated previously, but without the NNN term. We also discuss the superconducting instability of the attractive KMH model that is driven by condensation of Cooperons.

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