23Na NMR evidence for charge order and anomalous magnetism in NaxCoO2

Oriented powder samples of NaxCoO2 are studied by 23Na NMR and SQUID magnetometry. In nominal 0.50相似文献   

Event-by-event net charge fluctuations

We present analyses of event-by-event dynamical net charge fluctuations measured in 130 and 200 GeV Au+Au collisions with the STAR detector. The dynamical net charge fluctuations are evaluated using the ν _+-,dyn observable. Dynamical fluctuations measured in Au+Au collisions at 130 and 200 GeV are finite, and exceed charge conservation limits. They deviate from a perfect 1/N scaling and provide an indication that the collision dynamics varies with collision centrality.     

Net charge fluctuations at RHIC

We present measurements of dynamical net charge fluctuations in Au+Au collisions at $\sqrt {s_{NN} } = 20$ , 62, 130 and 200 GeV using the measure ν _+?,dyn. We observe the dynamical fluctuations are finite at all energies, and do not exhibit dependence on beam energy. We find net charge fluctuations violate the trivial 1/N scaling expected for nuclear collisions consisting of independent nucleon-nucleon interactions. We also find dynamical fluctuations exhibit sizable dependence of the pseudo-rapidity and azimuthal ranges of integration. We compare measured data with transport models and a toy model invoking radial flow, and show the bulk of the measured correlations can be accounted for by resonance production and radial collective flow.     

Correlation between quantum charge fluctuations and magnetic ordering in multiferroic LuFe<Subscript>2</Subscript>O<Subscript>4</Subscript>

We examine the interplay between quantum charge fluctuations and magnetic ordering in multiferroic LuFe₂O₄ and show that this can couple spin and charge degrees of freedom in a LuFe₂O₄ bilayer below the Neel temperature T _N . Our analysis supports the idea that the double exchange mechanism normally used in metallic systems can be applied to charge-ordered insulators. This causes ferrimagnetic spin order to reduce the transfer integrals between Fe²⁺ and Fe³⁺ in LuFe₂O₄, decreasing charge fluctuations and increasing the polarization in this system below T _N . This work thus provides a more detailed understanding of the mechanism for spin-charge coupling in LuFe₂O₄.     

Absence of charge fluctuations of europium in metallic single crystals of EuCu2Si2

The ¹⁵¹Eu Mössbauer effect study in the temperature range 2.2–299.5 K on pulverized single crystals of EuCu₂Si₂ synthesized from an indium flux is presented. In contrast to previous studies on polycrystalline samples in which valence fluctuations for Eu were reported, we find that the Eu atoms are divalent in the whole temperature range. Therefore, there are no charge fluctuations of Eu in EuCu₂Si₂.     

The charge fluctuations in classical Coulomb systems

We study the asymptotic behavior of the charge fluctuations (Q – (Q )² in infinite classical systems of charged particles, and show, under certain clustering assumptions, that if the charge fluctuations are not extensive, then they are necessarily of the order of the surface ¦¦. Moreover, when the canonical sum rules that are typical for equilibrium states of particles interacting with long-range forces hold true, we prove a central limit theorem for the normalized charge variable ¦¦^–1/2((Q – (Q )) in two and three dimensions. In one dimension, the probability distribution of the charge itself converges. The latter case is illustrated by the example of the one-dimensional Coulomb gas.     

Large charge fluctuations in classical Coulomb systems

The typical fluctuation of the net electric chargeQ contained in a subregion of an infinitely extended equilibrium Coulomb system is expected to grow only as S, whereS is the surface area of. For some cases it has been previously shown thatQ/S has a Gaussian distribution as ¦¦. Here we study the probability law for larger charge fluctuations (large-deviation problem). We discuss the case when both ¦¦ andQ are large, but now withQ of an order larger than S. For a given value ofQ, the dominant microscopic configurations are assumed to be those associated with the formation of a double electrical layer along the surface of. The probability law forQ is then determined by the free energy of the double electrical layer. In the case of a one-component plasma, this free energy can be computed, for large enoughQ, by macroscopic electrostatics. There are solvable two-dimensional models for which exact microscopic calculations can be done, providing more complete results in these cases. A variety of behaviors of the probability law are exhibited.     

载荷波动在超导特性中的研究

利用超导体的金兹堡_朗道理论第一方程对超导体的特性作一些探讨研究.从理论上得出金兹 堡_朗道的载荷有效质量m也可以为负，在理论上得到超导能量以及超导体电流密度和超导自 由能与温度、载荷密度的具体表达式，并且可以拟合实验结果. 关键词： 超导电性 电流密度 载荷密度     

Coherent structures in presence of dust charge fluctuations

This paper shows the formation of nonlinear coherent structures in a dusty plasma in presence of dust charge fluctuations. Using the typical plasma parameters the potential of the nonlinear coherent structures is derived.     

NMR evidence for the charge transfer from interstitial NO or O2 to molecule C60 in solid C60

Solid C₆₀ was stored in NO and O₂ under high pressure, and the molecule NO and O₂ were found to diffuse into the octahedral interstitial sites in its fcc crystal lattice. Their ¹³C NMR MAS spectra composed of a primary resonance at 143.7 ppm, accompanied by several minor peaks shifted downfield respectively. The spectra at various temperatures from 210 to 300 K have been measured, and the chemical shifts of the minor peaks referenced to the primary resonance versus inverse temperature show straight lines. But, the lines do not go through origin, and their intercepts are equal to 0.13 ppm or its multiple. Due to a non-zero intercept at high-temperature limit, we proposed that there is a charge transfer from NO and from O₂ to C₆₀. The quantity of the charge transferred has been calculated, that is about 0.065 q_e^- (q_e^- for the elementary charge on an electron).     

59Co NMR evidence for charge ordering below T_(CO) approximately 51 K in Na0.5CoO2

The CoO2 layers in NaxCoO2 may be viewed as a spin S=1/2 triangular-lattice doped with charge carriers. The underlying physics of the cobaltates is very similar to that of the high T_(c) cuprates. We will present unequivocal 59Co NMR evidence that below T_(CO) approximately 51 K, the insulating ground state of the itinerant antiferromagnet Na0.5CoO2 (T_(N) approximately 86 K) is induced by charge ordering.     

Dynamical behaviour of stochastic dust charge fluctuations

The dynamics of stochastic dust charge fluctuations is investigated. An inhomogeneous Burgers equation with a linear forcing term is derived in which the Burgers term is proportional to the diffusivity of dust charge fluctuations. This novel equation is solved analytically. Possibility of turbulence due to stochastic charge fluctuations is highlighted.     

NMR evidence for triple-q multipole structure in NpO2

In order to elucidate the nature of the exotic ordered phase of NpO2 below T(0)=26 K, we have initiated the first 17O-NMR measurements on this system. From the 17O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below T0. It has also been shown that the characteristic features of the hyperfine interaction at the oxygen sites are well explained by invoking a hyperfine interaction with field-induced antiferromagnetic moments which appear as a result of the triple-q antiferroquadrupolar order. The NMR findings strongly support the occurrence of the longitudinal triple-q multipole structure in NpO2.     

Magnetic structure of low-dimensional LiCu2O2 multiferroic according to 63,65Cu and 7Li NMR studies

The complex NMR study of the magnetic structure of LiCu₂O₂ multiferroic has been performed. It has been shown that the spin spirals in LiCu₂O₂ are beyond the ab, bc, and ac crystallographic planes. The external magnetic field applied along the c axis of the crystal does not change the spatial orientation of spirals in Cu²⁺ chains. A magnetic field of H ₀ = 94 kOe applied along the a and b axes rotates the planes of spin spirals in chains, tending to orient the normal n of spirals along the external magnetic field. The rotation angle of the planes of the magnetic moments are maximal at H ₀ ?? b.     

Baryon and electric charge fluctuations at crossover

We discuss the higher order cumulants of net-baryon and electric charge fluctuations as a probe of the QCD crossover. The sensitivity of the higher order cumulants in the hadron resonance gas model to an inclusion of repulsive interactions is also considered.     

An analytical formula for fluctuations in nuclear charge density

The experimental charge densities of atomic nuclei show fluctuations in their distributions.This paper investigates the limits of accuracy of two-parameter Fermi and three-parameter Fermi distributions in describing the charge density.An improved analytical function for density distribution is proposed,which allows for density fluctuation.The experimental charge densities of~(40)Ca,~(60)Ni,~(100)Mo,~(152)Sm and~(208)Pb,representing the various shapes of density fluctuation,are used to assess the accuracy of the proposed formula.The proposed function reproduces the experimental charge densities with significant improvement in accuracy over other commonly used formulae.A compilation of charge density distribution parameters of 73 nuclei is presented based on the proposed formula.     

Effects of nuclear charge fluctuations on dilepton photoproduction

Fluctuations of dilepton production from two photon interactions γγ→l~+l~- are studied in semicentral and peripheral nuclear collisions.Based on the Weizsacker-Williams approach,electromagnetic(EM) fields generated by moving nuclear charges are approximated as quasi-real photons.As fluctuating EM fields in each collision event are hard to be measured directly in experiments due to its short lifetime,we study the dilepton photoproduction with fluctuating EM fields,which are crucial for the EM fields induced chiral and charged particle evolutions,and calculate the relative standard deviation of the dilepton mass spectrum with the event-by-event fluctuating nuclear charge distributions.This fluctuation effect becomes smaller in more peripheral collisions where the shift of proton positions is implicit for EM fields outside the nucleus.The uncertainty of effective impact parameter △b on the standard deviation is also studied,and its effect is around one-third of the effect of nuclear charge fluctuations when △b is taken as～1 fm.     

Real-time renormalization group and charge fluctuations in quantum dots

We develop a perturbative renormalization-group method in real time to describe nonequilibrium properties of discrete quantum systems coupled linearly to an environment. We include energy broadening and dissipation and develop a cutoff-independent formalism. We present quantitatively reliable results for the linear and nonlinear conductance in the mixed-valence and empty-orbital regime of the nonequilibrium Anderson impurity model with finite on-site Coulomb repulsion.