ELECTRONIC PROPERTIES OF STRONGLY CORRELATED SYSTEMS

1988 ◽  
Vol 02 (05) ◽  
pp. 627-629 ◽  
Author(s):  
T. M. RICE ◽  
F. C. ZHANG
Keyword(s):  
Nearest Neighbor ◽  
Energy Scale ◽  
Strongly Correlated ◽  
Effective Hamiltonian ◽  
Coupling Constant ◽  
Excitation Energies ◽  
A Value ◽  
Spin Singlet ◽  
Hybridization Energy ◽  
Hilbert Subspace

The observation that the energy scale of the magnetic excitations determined by the Heisenberg coupling constant ( J ≈ 0.1eV ) is much smaller than the charge excitation energies (≳ 2eV ) places the stoichiomatic Cu-oxides with formal valence Cu 2+ in the class of Mott insulators. Holes introduced into the CuO 2 layers can therefore be described by an effective Hamiltonian which contains a hopping term for holes between nearest neighbor CuO 4-squares (matrix element, t ) in addition to the Heisenberg term1). This effective Hamiltonian is restricted to the Hilbert subspace with one or less electrons in the Wannier orbital on each CuO 4 square. The Wannier orbital is made up from the [Formula: see text] Cu-orbital and a combination of the 2p O-orbitals with the same symmetry. The hybridization energy is maximized for a hole by forming a spin singlet combination of these orbitals so that the form of the effective Hamiltonian does not differ in form2) from that of a single band Hubbard model in the strongly correlated limit. The inclusion of O-O hopping does not change this conclusion3). Estimates of the parameter t , give a value t ≈ 0.5eV so that the ratio J/t ≪ l .

Effects of Light on Schooling and Feeding of Jack Mackerel, Trachurus symmetricus

1968 ◽  
Vol 25 (2) ◽  
pp. 393-407 ◽  
Author(s):  
John R. Hunter
Keyword(s):  
Motion Picture ◽  
Nearest Neighbor ◽  
Motion Pictures ◽  
Separation Distance ◽  
The Other ◽  
Angular Deviation ◽  
Jack Mackerel ◽  
A Value

Schools of six jack mackerel each were photographed with infrared film at eight levels of luminance and also in darkness. Three indices were used to measure the behavior of the school from motion pictures. Two of the indices, mean distance to nearest neighbor and mean separation distance, were measures of the distances between individuals in a school; the other, mean angular deviation, was a measure of differences in orientation between individuals. A value for each index was calculated for each motion picture frame.From 12.1 to 6 × 10−6 ft-L no differences existed in the angular deviation of the school or in the distances between fish. At 6 × 10−7 ft-L the intervals between fish were much larger than at higher levels of brightness and groups showed little uniformity in their orientation. Below 6 × 10−7 ft-L (darkness) schools were dispersed and the distributions of values of angular deviation were random.The ability of jack mackerel to feed on live adult Artemia was also tested at eight levels of luminance and in darkness. The number of Artemia eaten at 6 × 10−5 ft-L was about half of that eaten at the normal daytime level of 12.1 ft-L. Few Artemia were eaten at 6 × 10−7 ft-L and none in darkness.Comparison of these data with measurements of light in the sea indicated that jack mackerel probably would be able to maintain schools near the surface on a moonless starlit night and that they probably could feed effectively near the surface on a full moonlight night.

scholarly journals Effective Hamiltonian for a half-filled asymmetric ionic Hubbard chain with alternating on-site interaction

2016 ◽  
Vol 30 (03) ◽  
pp. 1550260 ◽  
Author(s):  
I. Grusha ◽  
M. Menteshashvili ◽  
G. I. Japaridze
Keyword(s):  
Magnetic Field ◽  
Nearest Neighbor ◽  
Effective Hamiltonian ◽  
Heisenberg Chain ◽  
Spin Hamiltonian ◽  
Effective Spin ◽  
One Dimensional ◽  
The One ◽  
Strong Repulsion ◽  
Ionic Hubbard Model

We derive an effective spin Hamiltonian for the one-dimensional half-filled asymmetric ionic Hubbard model (IHM) with alternating on-site interaction in the limit of strong repulsion. It is shown that the effective Hamiltonian is that of a spin S = 1/2 anisotropic XXZ Heisenberg chain with alternating next-nearest-neighbor (NNN) and three-spin couplings in the presence of a uniform and a staggered magnetic field.

Optical properties of complex oxides: Vanadate ladders and related inorganic nanotubes

2002 ◽  
Vol 12 (9) ◽  
pp. 355-355
Author(s):  
J. L. Musfeldt ◽  
A. B. Sushkov ◽  
J. Jegoudez ◽  
A. Revcolevschi ◽  
P. Millet ◽  
...  
Keyword(s):  
Phase Boundary ◽  
Degrees Of Freedom ◽  
Energy Scale ◽  
Coupling Constant ◽  
Field Phase ◽  
Inorganic Nanotubes ◽  
Small Coupling ◽  
Small Coupling Constant ◽  
Na Ions ◽  
T Phase

Optical spectroscopy is a sensitive probe of charge, spin, and lattice degrees of freedom. In this talk, I will detail our magneto-optical work on alpha'-NaV2O5, a prototypical ladder material, as well as the new Na2V3O7 nanotubes. Using changes in electronic structure with temperature and applied magnetic field, we have mapped out the H-T phase diagram of alpha'-NaV2O5. We find a temperature independent phase boundary at 27 T which persists above Tc (34 K), a kink in Tc(H) near 27 T, and H$\wedge $2 behavior of Tc(H) in the high field phase with an unusually small coupling constant. The energy scale of Tc and the newly discovered phase boundary at Hc (27 T) are identical. Confinement effects are investigated in the related nanotubes. Results include a larger gap than in analogous bulk materials as well as a low-energy rattling mode, which corresponds to the motion of Na+ ions inside the nanotube.

scholarly journals Information Retrieval Document Classified with K-Nearest Neighbor

2018 ◽  
Vol 1 (2) ◽  
pp. 129 ◽  
Author(s):  
Alifian Sukma ◽  
Badruz Zaman ◽  
Endah Purwanti
Keyword(s):  
Information Retrieval ◽  
Evaluation System ◽  
Nearest Neighbor ◽  
Technology Development ◽  
Health Science ◽  
Cosine Similarity ◽  
K Nearest Neighbor ◽  
Physical Sciences ◽  
Social Sciences And Humanities ◽  
A Value

Along with the rapid advancement of technology development led to the amount of information available is also increasingly abundant. The aim of this study was to determine how the implementation of information retrieval system in the classification of the journal by using the cosine similarity and K-Nearest Neighbor (KNN).The data used as many as 160 documents with categories such as Physical Sciences and Engineering, Life Science, Health Science, and Social Sciences and Humanities. Construction stage begins with the use of text mining processing, the weighting of each token by using the term frequency-inverse document frequency (TF-IDF), calculate the degree of similarity of each document by using the cosine similarity and classification using k-Nearest Neighbor.Evaluation is done by using the testing documents as much as 20 documents, with a value of k = {37, 41, 43}. Evaluation system shows the level of success in classifying documents on the value of k = 43 with a value precision of 0501. System test results showed that 20 document testing used can be classified according to the actual category

scholarly journals Ferromagnetism out of charge fluctuation of strongly correlated electrons in κ-(BEDT-TTF)2Hg(SCN)2Br

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Minoru Yamashita ◽  
Shiori Sugiura ◽  
Akira Ueda ◽  
Shun Dekura ◽  
Taichi Terashima ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Strongly Correlated Electrons ◽  
Charge Order ◽  
Charge Fluctuation ◽  
Spin Moment ◽  
Strongly Correlated ◽  
Weiss Temperature ◽  
Torque Measurements ◽  
Spin Singlet ◽  
Insulating Phase

AbstractWe perform magnetic susceptibility and magnetic torque measurements on the organic κ-(BEDT-TTF)2Hg(SCN)2Br, which is recently suggested to host an exotic quantum dipole-liquid in its low-temperature insulating phase. Below the metal-insulator (MI) transition temperature, the magnetic susceptibility follows a Curie–Weiss law with a positive Curie–Weiss temperature, and a particular $$M\propto \sqrt{H}$$ M ∝ H curve is observed. The emergent ferromagnetically interacting spins amount to about 1/6 of the full spin moment of localized charges. Taking account of the possible inhomogeneous quasi-charge-order that forms a dipole-liquid, we construct a model of antiferromagnetically interacting spin chains in two adjacent charge-ordered domains, which are coupled via fluctuating charges on a Mott-dimer at the boundary. We find that the charge fluctuations can draw a weak ferromagnetic moment out of the spin singlet domains.

scholarly journals Rb, Rc and New Physics: An Updated Model Independent Analysis

1997 ◽  
Vol 12 (04) ◽  
pp. 723-742 ◽  
Author(s):  
P. Bamert
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
New Physics ◽  
Low Energy ◽  
Coupling Constant ◽  
A Value ◽  
Independent Analysis ◽  
The Standard Model ◽  
Necessary And Sufficient ◽  
Do So

We analyze LEP and SLC data from the 1995 Summer Conferences as well as from low energy neutral current experiments for signals of new physics. The reasons for doing this are twofold: first to explain the deviations from the Standard Model observed in Rb and Rc and second to constrain nonstandard contributions to couplings of the Z0 boson to all fermions and to the oblique parameters. We do so by comparing the data with the Standard Model as well as with a number of test hypotheses concerning the nature of the new physics. These include nonstandard [Formula: see text]-, [Formula: see text]- and [Formula: see text]-couplings as well as the couplings of the Z0 to fermions of the entire first, second and third generations and universal corrections to all up- and down-type quark couplings (as can arise see for example in Z' mixing models). We find that nonstandard [Formula: see text] couplings are both necessary and sufficient to explain the data and in particular the Rb anomaly. It is not possible to explain Rb, Rc and a value of the strong coupling constant consistent with low energy determinations invoking only nonstandard [Formula: see text]- and [Formula: see text]-couplings. To do so one has to have also new physics contributions to the [Formula: see text] or universal corrections to all [Formula: see text] couplings.

scholarly journals Sub-GeV-scale signatures of hidden braneworlds up to the Planck scale in a SO(3,1)-broken bulk

2019 ◽  
Vol 34 (05) ◽  
pp. 1950029 ◽  
Author(s):  
Coraline Stasser ◽  
Michaël Sarrazin
Keyword(s):  
Standard Model ◽  
Phenomenological Model ◽  
Quantum Dynamics ◽  
Scale Up ◽  
Planck Scale ◽  
Energy Scale ◽  
Beyond The Standard Model ◽  
Coupling Constant ◽  
The Standard Model ◽  
Gut Scale

Many-brane Universes are at the heart of several cosmological scenarios related to physics beyond the Standard Model. It is then a major concern to constrain these approaches. Two-brane Universes involving [Formula: see text]-broken 5D bulks are among the cosmological models of interest. They also allow considering matter exchange between branes, a possible way to test these scenarios. Neutron disappearance (reappearance) toward (from) the hidden brane is currently tested with high-precision experiments to constrain the coupling constant [Formula: see text] between the visible and hidden neutron sectors. When dealing with the sub-GeV-scale quantum dynamics of fermions, any pair of braneworlds can be described by a noncommutative two-sheeted space–time [Formula: see text] from which [Formula: see text] emerges. Nevertheless, the calculation of the formal link between [Formula: see text] for a neutron and [Formula: see text]-broken 5D bulks remains an open problem until now although necessary to constrain these braneworld scenarios. Thanks to a phenomenological model, we derive [Formula: see text] — for a neutron — between the two braneworlds endowed with their own copy of the Standard Model in an [Formula: see text]-broken 5D bulk. Constraints on interbrane distance and brane energy scale (or brane thickness) are discussed. While brane energy scale below the GUT scale is excluded, energy scale up to the Planck limit allows neutron swapping detection in forthcoming experiments.

scholarly journals A TOY MODEL OF THE FIVE-DIMENSIONAL UNIVERSE WITH THE COSMOLOGICAL CONSTANT

2004 ◽  
Vol 19 (29) ◽  
pp. 5051-5084
Author(s):  
WOJCIECH TARKOWSKI
Keyword(s):  
Cosmological Constant ◽  
Zero Point ◽  
Einstein Equations ◽  
Vacuum Energy Density ◽  
Coupling Constant ◽  
Virtual Particles ◽  
A Value ◽  
Proposed Model ◽  
Intrinsic Angular Momentum ◽  
Energy Cutoff

A value of the cosmological constant in a toy model of the five-dimensional universe is calculated in such a manner that it remains in agreement with both astronomical observations and the quantum field theory concerning the zero-point fluctuations of the vacuum. The (negative) cosmological constant is equal to the inverse of the Planck length squared, which means that in the toy model the vanishing of the observed value of the cosmological constant is a consequence of the existence of an energy cutoff exactly at the Planck level. In turn, a model for both a virtual and a real particle–antiparticle pair is proposed which describes properly some energetic properties of both the vacuum fluctuations and created particles, as well as it allows one to calculate the discrete "bare" values of an elementary particle's mass, electric charge and intrinsic angular momentum (spin) at the energy cutoff. The relationships between the discussed model and some phenomena such as the Zitterbewegung and the Unruh–Davies effect are briefly analyzed, too. The proposed model also allows one to derive the Lorentz transformation and the Maxwell equations while considering the properties of the vacuum filled with the sea of virtual particles and their antiparticles. Finally, the existence of a finite value of the vacuum-energy density resulting from the toy model leads us to the formulation of dimensionless Einstein equations which may be derived from the Lagrangian with a dimensionless (naively renormalized) coupling constant.

scholarly journals GINZBURG–LANDAU LIKE THEORY OF HIGH TEMPERATURE SUPERCONDUCTIVITY IN THE CUPRATES: EMERGENT d-WAVE ORDER

2012 ◽  
Vol 26 (10) ◽  
pp. 1230005
Author(s):  
T. V. RAMAKRISHNAN
Keyword(s):  
High Temperature ◽  
Cooper Pair ◽  
Nearest Neighbor ◽  
High Temperature Superconductivity ◽  
Transition Curve ◽  
Hole Doping ◽  
Positive Interaction ◽  
Long Wavelength ◽  
Spin Singlet ◽  
D Wave

High temperature superconductivity in the cuprates remains one of the most widely investigated, constantly surprising and poorly understood phenomena in physics. Here, we describe briefly a new phenomenological theory inspired by the celebrated description of superconductivity due to Ginzburg and Landau and believed to describe its essence. This posits a free energy functional for the superconductor in terms of a complex order parameter characterizing it. We propose that there is, for superconducting cuprates, a similar functional of the complex, in plane, nearest neighbor spin singlet bond (or Cooper) pair amplitude ψij. Further, we suggest that a crucial part of it is a (short range) positive interaction between nearest neighbor bond pairs, of strength J′. Such an interaction leads to nonzero long wavelength phase stiffness or superconductive long range order, with the observed d-wave symmetry, below a temperature Tc~z J′ where z is the number of nearest neighbors; d-wave superconductivity is thus an emergent, collective consequence. Using the functional, we calculate a large range of properties, e.g., the pseudogap transition temperature T* as a function of hole doping x, the transition curve Tc(x), the superfluid stiffness ρs(x, T), the specific heat (without and with a magnetic field) due to the fluctuating pair degrees of freedom and the zero temperature vortex structure. We find remarkable agreement with experiment. We also calculate the self-energy of electrons hopping on the square cuprate lattice and coupled to electrons of nearly opposite momenta via inevitable long wavelength Cooper pair fluctuations formed of these electrons. The ensuing results for electron spectral density are successfully compared with recent experimental results for angle resolved photo emission spectroscopy (ARPES), and comprehensively explain strange features such as temperature dependent Fermi arcs above Tc and the "bending" of the superconducting gap below Tc.

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′.

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