Charge Expulsion, Spin Meissner Effect, and Charge Inhomogeneity in Superconductors

Superconductivity occurs in systems that have a lot of negative charge: the highly negatively charged (CuO₂)⁼ planes in the cuprates, negatively charged (FeAs)⁻ planes in the iron arsenides, and negatively charged B ⁻ planes in magnesium diboride. And, in the nearly filled (with negative electrons) bands of almost all superconductors, as evidenced by their positive Hall coefficient in the normal state. No explanation for this charge asymmetry is provided by the conventional theory of superconductivity, within which the sign of electric charge plays no role. Instead, the sign of the charge carriers plays a key role in the theory of hole superconductivity, according to which metals become superconducting because they are driven to expel negative charge (electrons) from their interior. This is why NIS tunneling spectra are asymmetric, with larger current for negatively biased samples. The theory also offers a compelling explanation of the Meissner effect: as electrons are expelled towards the surface in the presence of a magnetic field, the Lorentz force imparts them with azimuthal velocity, thus generating the surface Meissner current that screens the interior magnetic field. In type II superconductors, the Lorentz force acting on expelled electrons that do not reach the surface gives rise to the azimuthal velocity of the vortex currents. In the absence of applied magnetic field, expelled electrons still acquire azimuthal velocity, due to the spin–orbit interaction, in opposite direction for spin-up and spin-down electrons: the “Spin Meissner effect.” This results in a macroscopic spin current flowing near the surface of superconductors in the absence of applied fields, of magnitude equal to the critical charge current (in appropriate units). Charge expulsion also gives rise to an interior outward-pointing electric field and to excess negative charge near the surface. In strongly type II superconductors this physics should give rise to charge inhomogeneity and spin currents throughout the interior of the superconductor, to large sensitivity to (non-magnetic) disorder and to a strong tendency to phase separation.     

分层装药对杆式射流的影响分析

为了研究分层装药结构的内、外层炸药材料、装药厚度对杆式射流成型的影响,利用True Grid和LSDYNA软件对不同工况下杆式射流的成型进行数值模拟。仿真结果表明:分层装药对杆式射流的影响与内、外层装药的爆速差△D和厚度比d_1/d_2有关,当d_1/d_24.4时,装药的爆速差△D对射流的增益效果成正相关;当4.4d_1/d_28.0时,分层装药对射流无明显影响;当d_1/d_28.8时,爆速差△D与射流的增益效果呈负相关。总体上,分层装药结构对射流形态、整体动能和头、尾速度有优化增益作用,且优化和增益效果与内、外层装药的厚度比及材料有关,合理的装药材料以及装药比例能够有效提高杆式射流的毁伤效能。     

Charge motion in solid argon

The measurement of currents induced in solid argon by a radioactive source is described. The results show evidence of negative and positive charge motion. In one sample small bubbles were observed at the interface between solid and anode at a threshold field. The movement of these bubbles shows the possibility of mass transport through solid argon.     

Charge Transfer in Fullerene Films

Abstract

The conductivity of C₆₀ films in the temperature range of 100-300 K is determined by the jumps over localized states in the energy region of 1.5 ? 2.0 eV. At T > 350 K the activation energy of conductivity is determined by the laws of charge transfer over delocalized states. At T > 350 K the optical width of the forbidden band coincides with the mobility edge.     

Charge trapping in MOS systems

Measurements on MOS capacitors and MOS transistors at room temperature and 77 K lead to the conclusion that large slow-trapping effects can occur at the Si-SiO₂ interface at room temperature. These “slow state” effects differ substantially from the “slow state” effects usually observed in the Si-SiO₂ system.     

Charge trapping in polymer diodes

We report studies focusing on the nature of trap states present in single layer ITO/poly(phenylene vinylene)/Al light emitting diodes. At high applied bias the IV characteristics from 11 to 290 K can be successfully modelled by space charge limited current (SCLC) theory with an exponential trap distribution, giving a trap density H_t of 4(±2) × 10¹⁷ cm⁻³, μ_p, between 10⁻⁶ and 5 × 10⁻⁸ cm² V⁻¹ s⁻¹ and a characteristic energy E_t of 0.15 eV at high temperatures. The transient conductance follows a power-law relationship with time whose decay rate decreases with decreasing temperature. This can be directly related to the emptying of the trap distribution found in the SCLC analysis. Due to variations in structure, conformation and environment, the polymer LUMO and HOMO density of states form Gaussian distributions of chain sites. The deep sites in the tail of the distributions are the observed traps for both positive and negative carriers. The same sites dominate the photo- and electroluminescence emission. This implies that the emissive layer in organic LED's should be made as structurally disordered as possible.     

钙钛矿锰氧化物中电荷有序现象研究进展

电荷有序现象在混价过渡金属氧化物中早有研究, 钙钛矿锰氧化物中由于电荷有序与自旋有序、轨道有序、晶格畸变等相互关联而特别引人注目. 本文综述了有关电荷有序现象的早期 研究与近期进展, 重点介绍了电荷有序转变附近的一些物理异常现象与影响电荷有序态稳定的有关因素.     

Charge transfer luminescence in Yb-containing compounds

The characteristics of charge transfer transition of Yb³⁺ in selected compounds and complexes are reviewed. Systematic comparison of the optical and luminescence spectra as well as the decay kinetics of Yb-doped aluminium perovskites and garnets is provided. Effect of intrinsic defects and possible occurrence of Yb²⁺ is discussed and possible application areas are briefly mentioned.     

Charge exchange in low-energy ion-surface scattering

Charge exchange between low-energy projectiles and solid materials is explored for systems in which there is overlap between the ionization level and the surface bands. Time-of-flight spectroscopy is used to measure the charge state and kinetic energy distributions of scattered and recoiled atomic particles. Alkali ions scattered from alkali and halogen adatoms have larger neutralization probabilities than for scattering from the substrate, indicating that they both have positively charged regions at the top, which is surprising for the negatively charged halogen adsorbates. Because of strong overlap, Na⁺ ions scattered from Au nanocrystals neutralize by interaction with the quantum-confined states. Charge exchange in symmetric systems was investigated by measurements of the charge state of Al emitted from clean Al(1 0 0) by direct recoil induced by 5 keV Xe⁺ ions. The neutralization of recoiled Al is basically consistent with a resonant process resulting from the overlap of the Al atomic and solid states.     

Charge Complementarity and Interlayer Coupling Between Charge Ordered Layers of Cuprates

The interlayer Coulomb coupling between charge ordered superlattices with charge antisymmetry has been studied. The 2D pair-condensate can be characterized by a charge ordered state with a checkerboard like pattern seen recently by scanning tunneling microscopy. Interlayer charge complementarity is essential for getting interlayer energy gain which is found to be proportional to the condensation energy. The correlation between the condensation energy and the critical temperature is studied within our charge ordered superlattice bilayer model in which pairing is supported by interlayer Coulomb energy gain (potential energy-driven superconductivity). The static c-axis dielectric constant _c is calculated for various cuprates and compared with the available experimental data.     

Charge Transport in Solid 4He

With the help of a new experimental technique strong anisotropy of the mobility of ions has been observed in hcp ⁴ He crystals. The mobility of positive ions in the direction of the six-fold axis is found to be 200 times higher than in the perpendicular direction. Activation energies of the mobility have been measured in both principal directions. They are equal to: 5.3K in the direction of the C₆-axis and 11K in the perpendicular direction. The behaviour of the ions' velocity in the strong electric field regime is also studied as a function of the orientation.     

Charge Transport in Unconventional Superconductor Junctions

We report two remarkable recent topics about zero-bias conductance peak (ZBCP) in normal-metal/unconventional superconductor junctions. We show that the roughness at a surface of superconductors strongly suppresses the ZBCP when the transparency of the interface is sufficiently low. In a numerical simulation at a zero-magnetic field, we confirm the split of the ZBCP owing to the interfacial roughness in realistic band structures of the high-T _c superconductors. We also study the influence of a magnetic field H on the zero bias conductance peak (ZBCP). For p-wave junctions, ZBCP does not split into two by H even for sufficiently low transparent junctions, where ZBCP clearly splits for d-wave. This unique property originates from the fact that for p-wave superconductors, perpendicularly injected quasiparticle form ZES, which contributes most dominantly on the tunneling conductance. We propose that tunneling spectroscopy in the presence of magnetic field, i.e., magnetotunneling, is a promising method to determine the pairing symmetry of unconventional superconductors.     

增效射孔中火药装药的实验研究

文章介绍了一种增效射孔弹模拟靶试验装置。并用该装置测得了在装药量相同的情况下,增面燃烧火药,减面燃烧火药以及复合装药的枪内压力时间曲线。同时讨论了在装药量变化时,枪内压力时间曲线的变化。     

The Crucial Interplay Between Spin, Charge and Lattice in Organic Superconducting Charge Transfer Salts

Even though superconductivity in organic charge transfer salts (CTS) is unconventional since evidence for a d-wave order parameter is seen , lattice effect play a crucial role, because isotope effects have been observed as well as substantial influences of the insulating buffer layers on the material properties. Consequently, models for CTS should not only take strong correlations into account but also consider spin, charge lattice interaction effects together with a-axis coupling arising from the anionic buffer layers. Here, we propose a novel model, where these latter effects are incorporated and various experimental findings consistently explained.