Top PDF The infinite range Heisenberg model and high temperature superconductivity

Correlated Electron Systems and High Temperature Superconductivity

Correlated Electron Systems and High Temperature Superconductivity

indeed enhanced and is increased as the system size increases in the 2D Hubbard model. The enhancement ratio increases almost linearly  L as the system size is increased, which is an indication of the existence of superconductivity. Our criterion is that when the en- hancement ratio as a function of the system size L is proportional to a certain power of L , superconductivity will be developed. This ratio depends on U and is reduced as U is decreased. The dependence on the band filling shows a dome structure as a function of the electron density. In the 10 10  system, the ratio is greater than 1 in the range 0.3  n e  0.9 . Let us also mention on superconductivity at half-filling. Our results indicates the absence of superconductivity in the half-filling case because there is no enhancement of pair correlation functions
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An Improved Finite Temperature Lanczos Method and Its Application to the Spin 1/2 Heisenberg Model on the Kagome Lattice

An Improved Finite Temperature Lanczos Method and Its Application to the Spin 1/2 Heisenberg Model on the Kagome Lattice

In addition to this two-step strategy, we propose a sampling method for selecting the initial random state. It is well known that the random vector method is quite effective for the trace calculation of the partition function. If the Hamiltonian has some symmetry, the basis states are divided into symmetry sectors. In each symmetry sec- tor we calculate the partition function. At the infinitely high T a sampling weight of each symmetry sector is proportional to the number of basis states in the symmetry sector. But at very low T , the partition function de- pends extremely on the lowest energy E s of the symmetry sector s . Based on this consideration, we use a product of exp ( − E T s 1 ) and the number of basis states for a sample weight of a sector.
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Superconductivity in ropes of carbon nanotubes

Superconductivity in ropes of carbon nanotubes

and long mean free path [9]. These properties make them long sought-after realizations of 1D conductors. In one dimension, repulsive electron-electron interactions lead to an exotic correlated electronic state, the Luttinger liquid (LL) [10, 11]. In a LL, collective plasmon- like excitations give rise to anomalies in the single-particle density of states, and long-range order cannot survive even at zero temperature. The low-energy theory of SWNTs [12, 13] predicts a metallic SWNT to constitute a realization of a four-channel LL, with channel index a = c+, c − , s+, s − corresponding to total/relative charge/spin degrees of freedom. These arise due to the K − K ′ degeneracy and the electronic spin. The interaction strength
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Long-range Heisenberg models in quasiperiodically driven crystals of trapped ions

Long-range Heisenberg models in quasiperiodically driven crystals of trapped ions

mark that, in order to obtain an analytical expression for even larger interaction ranges, one should take into account further terms in the approximation above Eq. (C5), which may be- come relevant for sufficiently-small detunings. In any case, such small MS detunings compromise the validity of a pure effective spin model, as errors due to a thermal phonon popu- lation start playing a dangerous role 10 .

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Theory on another type of temperature-independent superconductivity based on circuit approaches with high critical current density

Theory on another type of temperature-independent superconductivity based on circuit approaches with high critical current density

Using this macroscopic wave function, this paper describes the derived London equation. In this process, we introduce the concept of an internal toroid and its inductance L. Calculating the value of the above-mentioned inductance L, we introduce an equivalent circuit. Using this equivalent circuit and the PSIM software, the time dependences of the voltages and current on the sample can be found. As a result, the voltage of the sample converging to zero experiences a negative voltage immediately prior to the transition time, which is an evidence of the Meissner effect. Even though the values of the resistances and currents were varied, the result of our superconductivity with negative voltages remains.
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Classifying superconductivity in an infinite-layer nickelate Nd 0.8 Sr 0.2 NiO 2

Classifying superconductivity in an infinite-layer nickelate Nd 0.8 Sr 0.2 NiO 2

[5] Johnston D C, Prakash H, Zachariasen W H, Viswanathan R 1973 High temperature superconductivity in the LiTiO ternary system Materials Research Bulletin 8 777-784 [6] Sleight A W, Gillson J L, Bierstedt P E 1975 High-temperature superconductivity in the BaPb 1-x Bi x O 3 systems Solid State Communications 17 27-28

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Characterization of bagasse binderless particleboard manufactured in high-temperature range

Characterization of bagasse binderless particleboard manufactured in high-temperature range

shows the influence of pressing temperature on the MOE of bagasse and recycled chip binderless particleboard. The MOE improved with the increase of pressing temperature. For bagasse particleboard, a peak value of 3.51 GPa was recorded at the pressing temperature of 260 °C, which was twice as high of that at 200 °C. Recycled chip particle- board showed a peak value of 2.53 GPa at the pressing temperature of 280 °C. Both the MOR and MOE values of recycled chip particleboard were about 40 % lower than those of bagasse particleboard at every tested temperature. From these results, we conclude that the pressing temper- ature greatly influenced the bending properties of binder- less particleboards, and the optimum condition for the experiment was approximately 260 °C. The raw material type also affected the bending properties of the relevant board; particularly, favorable properties were observed for bagasse. Bagasse binderless particleboard manufactured at 260 °C exceeded the minimum permitted values for the MOE of 3 GPa for grade 18-type particleboard by JIS A 5908 and showed an equivalent value to that of the PMDI particleboard.
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Characterization of near-room-temperature superconductivity in yttrium superhydrides

Characterization of near-room-temperature superconductivity in yttrium superhydrides

as unconventional superconductor which is nicely matched the location of other NRT superhydrides in the Uemura plot. It is also shown the thermodynamic fluctuations of the order parameter amplitude is dominating factor which limits superconducting transition temperature in superhydrides of yttrium.

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Simulating the climate response to atmospheric oxygen variability in the Phanerozoic: a focus on the Holocene, Cretaceous and Permian

Simulating the climate response to atmospheric oxygen variability in the Phanerozoic: a focus on the Holocene, Cretaceous and Permian

vertical, 20 model levels are used which increase in depth from 10 m in the shallowest layer to 616 m in the deepest layer. A time step of 60 min is employed and the ocean and atmosphere components exchange required fields once per day. The ocean component is based on the Cox (1984) model, solving the full primitive equation set in three dimensions. A staggered Arakawa B grid is employed in both atmosphere and ocean models. Sea ice is treated as a zero thickness layer on the surface of the ocean grid. Ice is assumed to form at the base at a freezing point of − 1.8 ◦ C but can also form from freezing in ice leads and by falling snow. A simple pa- rameterisation of sea-ice dynamics is also employed (Gordon et al., 2000) and sea-ice formation due to convergence from drift being limited to 4 m thick. Sea-ice albedo is fixed at 0.8 for temperatures below −10 ◦ C, decreasing linearly to 0.5 at
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Monte carlo analysis of the temperature effect on the infinite multiplication factor for uo2 and uo2 puo2 lattices of kritz benchmarks

Monte carlo analysis of the temperature effect on the infinite multiplication factor for uo2 and uo2 puo2 lattices of kritz benchmarks

of the Sweden KRITZ reactor. To quantify the contribution of each component of the infinite multiplication factor to the temperature coefficient, calculations were performed for the three configurations of KRITZ benchmark at two temperatures: room temperature 20°C and an elevated temperature 245°C, using MCNPX which is a continuous energy Monte Carlo reference code for the ed for this work were processed by means of the 4, JENDL-3.3, JEFF-3.1, ENDF/B-VII, and VII.1. The performed studies on the temperature coefficient have shown an agreement d those obtained from the final report published by the OECD in 2005
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HEISENBERG S UNCERTAINTY PRINCIPLE IN HIGH SCHOOL CURRICULUM

HEISENBERG S UNCERTAINTY PRINCIPLE IN HIGH SCHOOL CURRICULUM

We can ask the question: should the uncertainty principle be in high school curriculum (profile classes)? The answer is affirmative (because of fast nanotechnology developing), but we should strike a happy medium, it means we should arrange a clear way of principle presentation, easily understood by pupils.

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Model Based Split Range Algorithm for the Temperature Control of a Batch Reactor

Model Based Split Range Algorithm for the Temperature Control of a Batch Reactor

After choosing the proper modelling solution by simula- tion, the resulting split-range algorithm was tested on the pilot plant. The results of the test measurement can be seen in Figure 13. During the test measurements, similar to the simulation, constant reaction heat was introduced to the reactor with a special loop design for the physical simulation of chemical reactions [11]. The most notable differences between the simulation and test measurement result are caused by the varying temperatures of the monofluid loops of the thermoblock, which remained constant during the simulation. The oscillation between 500 and 1000 seconds, where a near-zero valve opening would be needed, can be explained with the construction of the system and the lag of the control valve in that re- gion.
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Cold Electron Quantum Mechanical Model for Superconductivity

Cold Electron Quantum Mechanical Model for Superconductivity

The temperature of object is essentially a measure of the average energy of thermal motion of molecules and atoms. Heat transformation between molecules and atoms is realized through the interaction of electrons outside the nuc- leus. In traditional theory, the electrons are regarded as the heat conduction and heat radiation messenger or carrier, however, any hot meanings has not been given in itself, in other words, the concept of temperature of electron were regarded meaningless. Was that reasonable? Have any proof of electron that should have no temperature meaning? In statistical view, the temperature relates to a degree of confusion. Electrons are all in doing their own business in order. It doesn’t seem to make sense that the degree of confusion of electrons is almost unchanged after heat effect.
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Macroscopic Quantum System, Highly Correlated Electron State, and High Temperature Superconductivity in Iron Pnictides

Macroscopic Quantum System, Highly Correlated Electron State, and High Temperature Superconductivity in Iron Pnictides

It is known that a partial substitution (10 percent) of oxygen by fluorine in LaOFeAs accompaned by introduc- tion of additional electrons into the FeAs layer gives rise to superconductivity. It can be supposed that each in- troduced electron is paired with one of two unpaired electrons of As 3− participating in formation of 1e bonds. The pair formation breaks the 1e bond, bonding between the ions becomes purely ionic, and Fe 2+ gets an unoccupied electron state. The singlet pair localizes at As 3− and becomes a new unshared pair of As 3− (in addition to the un- shared one in its apical electron state). The bonding of the new pair with As 3− becomes much weaker than that of its parent unpaired electron due to enhanced Coulomb repulsion from the 2e bond pairs present in the As 3− coor- dination polyhedron (Figure 1(b) and Figure 7). It is quite possible that the new pair will even pass from the d 4 s state into a higher-energy As 3− state formed by adding a part of the p state (or even into a new d 4 p state).
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Solid State Synthesis of Hydrogen Storage Mg2Co Alloys via Bulk Mechanical Alloying

Solid State Synthesis of Hydrogen Storage Mg2Co Alloys via Bulk Mechanical Alloying

genation takes place only at higher temperature. In case when the hydrogenation and de-hydrogenation steps, working at higher temperatures, are excluded in the thermodynamic route at 633 K, the maximum hydrogen absorption is limited to 2.03 mass% lower than the theoretical amount. Hence, relatively high holding temperature is still necessary to obtain maximum hydrogen absorption equivalent to theoretical capacity for Mg 2 Co without chemical modifications.

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Finite infinite range inequalities in the complex plane

Finite infinite range inequalities in the complex plane

closed, w be an admissible weight function on E, and a be a fixed positive Borel measure defined on E.. We also continue the notation described in Section 2.[r]

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Orbital Approach to High Temperature Superconductivity

Orbital Approach to High Temperature Superconductivity

High temperature superconductivity (HTS) was discovered in 1986 by Bednorz and Műller [1]. Since then thousands of papers and more than four monographs have been written on this subject in attempts to explain the origin and nature of the phenomenon. Within the approximately thirty year period since then no mathematical theories have explained, or related, HTS to specific atoms in the Periodic Table. The ori- gin of HTS, or why it occurs specifically in cuprates, has not been given.

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Plaquette Valence Bond Theory of Cuprate High Temperature Superconductivity

Plaquette Valence Bond Theory of Cuprate High Temperature Superconductivity

spin state formation and the non-Fermi liquid charac- ter of the normal phase [6]. Unfortunately, details of his original approach, such as suppression of interlayer hopping in the normal phase as the main factor of super- conductivity, seems to contradict experimental data [11]. The latest version of the RVB theory is presented in [12]. We believe, that the main assumption of the strongly correlated limit as the base of understanding the high- temperature superconductivity is correct, as well as em- phasizing a crucial role of spin singlet states, but impor- tant details were missing. Below we present arguments for the thesis, that the minimal object of HTSC-theory is the plaquette in the so-called effective t, t 0 Hubbard model [13], rather than the conventional atomic limit typical for the theory of Mott insulators [6, 9]. The best practical realization of this atomic based theory is the dynamical mean-field theory (DMFT) [14]. The obvi- ous minimal generalization in the case of d x 2 −y 2 -wave
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Theoretical Study of the Interplay of Superconductivity and Magnetism in FeAs Based Superconductors

Theoretical Study of the Interplay of Superconductivity and Magnetism in FeAs Based Superconductors

perimental as well as theoretical views. Nowadays, understanding the mechanism of superconductivity in such system is one of the challenging research areas. According to reviews on iron based superconductors [2] [3], magnetic interactions are important for understanding the mechanism of superconductivity. Experimental ob- servation and theoretical prediction show that knowing the interplay of superconductivity and magnetism may suggest the possible mechanism of superconductivity.

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