Tunneling Spectra for Quasi–One-Dimensional Organic Superconductors

The tunneling conductance spectra of a normal metal/insulator/quasi–one-dimensional superconductor is calculated using the Blonder-Tinkham-Klapwijk formulation. The pairing symmetry of the superconductor is assumed to be p or d, and f-wave. It is found that there is a well-defined zero-bias peak in electron tunneling along the direction parallel to the chains or normal to these when the transmitted quasiparticles feel different sign of the pair potential. The actual line shape of the spectra is sensitive to the nodes of the pair potential on the Fermi surface.     

准一维纳米结构ZnO的制备研究进展

准一维纳米结构ZnO因其优良的光电性质,在制作纳米电子器件和纳米光电子器件等许多领域表现出巨大的应用潜力.对准一维纳米结构ZnO在衬底上的制备生长方法、性质及衬底的影响作了简要的叙述.     

Galvanomagnetic Phenomena in Layered Organic Conductors

The dependence of the resistance and the Hall field in organic metals with the quasi-two-dimensional electron energy spectrum on the magnetic field strength and orientation is analyzed in the strong field limit. The inter-plane resistance is shown to be strongly dependent on the of magnetic field orientation. When the angle between the field and the highly conducting plane is zero, the resistance increases linearly in a relatively wide field range. The angle dependence of magnetoresistance at small is nonmonotonic: it exhibits a local minimum and then a sharp peak around = 0. The Hall constant in strong magnetic field does not depend on the field orientation.     

Role of the Dimerized Gap Due to Anion Ordering in the Quantized Hall Phases of Quasi-One Dimensional Organic Conductors

The electrical resistivities and magnetoresistances (MR) of a radical ion salt (EDO-TTFBr₂)₂FeCl₄ and its diamagnetic analogue (EDO-TTFBr₂)₂GaCl₄ are investigated under pressures. The resistivity of the FeCl₄ salt shows two anomalies due to the successive transitions of the π-electron layer, and another anomaly coming from the long-range magnetic ordering of the FeCl₄ layer. For the GaCl₄ salt negative MR is observed in the low-field region, suggesting a decrease of the SDW gap by applying the magnetic field. The MR of the FeCl₄ salt shows two abrupt increases, which proves the presence of field-induced successive transitions in the composite π-d spin system. The field dependence of the MR of this salt can be qualitatively explained based on the frustrated magnetic structure of π- and d-electron spins interacting with each other.     

Hall Effect in Bulk‐Doped Organic Single Crystals

The standard technique to separately and simultaneously determine the carrier concentration per unit volume (N , cm^?3) and the mobility (μ) of doped inorganic single crystals is to measure the Hall effect. However, this technique has not been reported for bulk‐doped organic single crystals. Here, the Hall effect in bulk‐doped single‐crystal organic semiconductors is measured. A key feature of this work is the ultraslow co‐deposition technique, which reaches as low as 10^?9 nm s^?1 and enables us to dope homoepitaxial organic single crystals with acceptors at extremely low concentrations of 1 ppm. Both the hole concentration per unit volume (N , cm^?3) and the Hall mobility (μ_H) of bulk‐doped rubrene single crystals, which have a band‐like nature, are systematically observed. It is found that these rubrene single crystals have (i) a high ionization rate and (ii) scattering effects because of lattice disturbances, which are peculiar to this organic single crystal.     

Solitons and Their Arrays: From Quasi 1D Conductors to Stripes

We suggest a short review of literature on various solitonic lattices and individual solitons in quasi one-dimensional conductors. This information seems to be quite relevant to topics of stripes and their melted phases correspondingly. We shall quote also the latest experiments, which access solitons as elementary excitations in organic conductors and in charge density waves. We shall outline a theory for ordered phases, where solitons should acquire forms of combined topological configurations (kink-roton complexes). The extension of this picture to cuprates allows interpretation of the latest STM observations on local rod-like structures.     

Ultra High Pressure Application to Organic Conductors

Under pressures as high as 20 GPa at room temperature the electronic and structural properties of organic conductors were measured to search for interesting pressure regimes where novel electronic states were expected. Thermopower, two-probe electrical resistance and contraction of sample’s volume were measured on the organic conductors: ϑ-(BEDT-TTF)₂CsZn(SCN)₄, α-(BEDT-TTF)₂I₃, (BEDT-TTF)₂PF₆ and (BEDT-TTF)-TCNQ. All the materials exhibited a positive thermopower of the order of 10 μV/K. At about 4–7 GPa (crossover pressure P_x) sharp changes were found in the pressure dependence of electronic and mechanical properties of all the substances under consideration related probably to the structural changes under pressure.     

Ab initio Pseudopotential Band Calculation of Organic Conductors

We have calculated the band structures of organic conductors TTF-TCNQ and -(BEDT-TTF) ₂ I ₃ using the ab initio plane-wave pseudopotential method within the local-density approximation (LDA). The Fermi-surface shape and the origin of bands near the Fermi level are investigated for each compound.     

Effects of Spin Fluctuations and Superconductivity in Quasi-One-Dimensional Organic Conductors

We study the electronic states using the single band Hubbard model at half-filling. We treat the effects of the on-site Coulomb interaction by the fluctuation-exchange (FLEX) method, and calculate the phase diagram and physical properties. The calculated pressure dependence of the magnetic transition temperature coincides well with the experimental one. We also show that a pseudogap is formed in the density of states near the chemical potential and that the NMR relaxation rate increases on cooling in the low-temperature region, and that d-wave superconductivity appears next to the antiferromagnetic state.     

Superconducting and Charge Ordering Phases of Two-Dimensional Organic Conductors

In order to investigate relationships between superconducting phase and charge ordered one, the uniaxial strain method is applied to the superconducting salt α-(BEDT-TTF)₂NH₄Hg(SCN)₄ and the organic conductor α-(BEDT-TTF)₂CsCd(SCN)₄. Both salts preserve metallic states under a-axial strain and show insulating behaviours under c-axial strain. These results suggest that i) c-axial strain controls the electronic properties of the α-type salts, and ii) the insulating state in the vicinity of the superconducting phase of α-(BEDT-TTF)₂NH₄Hg(SCN)₄ is a charge ordered phase, as expected from the comparison in the lattice parameters with the charge ordered salt θ-(BEDT-TTF)₂RbZn(SCN)₄.     

Pressure Effect on BDA-TTP Conductors

The pressure-induced conducting behavior of the charge-transfer salts (BDA-TTP)₂X [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene; X = ClO₄·H₂O, ClO₄, BF₄·H₂O, BF₄, and I₃] has been investigated. With increasing pressure, the transition temperature to insulator observed in the ClO₄·H₂O, ClO₄, BF₄·H₂O, and BF₄ salts increases. On the other hand, the resistance of the I₃ salt as a function of temperature at 10.0 kbar shows a drop attributable to a superconducting transition with an onset at 4.5 K. The superconducting transition temperature (T_c) can reach 8.2 K by applying a pressure of 10.3 kbar, but gradually decreases with further increases in the pressure.     

有机导体及超导体的回顾与展望

有机固体是一门多学科交叉的新型研究领域。主要研究具有磁性,光导、电导等特殊性质的分析体系的设计、合成与应用。本文在前人工的基础上,对有机导体及有机超导体的发展历程、结构规律、导电性质作了总强;并对有机导体及超导体的单晶培养、晶体电导率的测量方法作了描述。目前,有机超导体的超导温度最高已达１２．８Ｋ,科学家除了改变不同的阴离子与现有的给体培养单晶外,还对现有的给体进行修饰和设计并合成了新的给体。本文     

Magnetic and Pairing Correlation Functions and Interchain Coherence in Quasi-One-Dimensional Dimerized Organic Conductors

We study how magnetic and pairing correlation evolves with an increasing interchain hopping integral and decreasing dimerization of intrachain hopping integrals, by applying the density matrix renormalization group (DMRG) method to a three-chain extended Hubbard model at quarter filling for quasi-one-dimensional organic conductors, (TMTTF) ₂ X and (TMTSF) ₂ X. Magnetic correlation changes from weakly coupled chains of large-amplitude spin density waves to an interchain-coherence-developed spin density wave. Pairing correlation increases, though it still decays exponentially owing to a charge gap for parameters considered here.     

Phase Transitions from Incoherent and from Coherent Metal Phases in Quasi-One-Dimensional Organic Conductors

We study effects of a preformed Mott gap and dimensionality on interchain one-particle coherence and spin-density-wave phase transitions in weakly-coupled dimerized quarter-filled Hubbard chains. A phase diagram is given, based on the two-loop perturbative renormalization-group (RG) approach together with the random phase approximation. Feedback effects of interchain processes on the umklapp process are examined by the 1 + expansion. We discuss relevance of the present result to the SDW phase transitions in the quasi-one-dimensional dimerized quarter-filled organic conductors, (TMTTF) ₂ X and (TMTSF) ₂ X.     

One-Dimensional Covalent Organic Framework as High-Performance Cathode Materials for Lithium-Ion Batteries

Covalent organic frameworks (COFs) have emerged as a new class of cathode materials for energy storage in recent years. However, they are limited to two-dimensional (2D) or three-dimensional (3D) framework structures. Herein, this work reports designed synthesis of a redox-active one-dimensional (1D) COF and its composites with 1D carbon nanotubes (CNTs) via in situ growth. Used as cathode materials for Li-ion batteries, the 1D COF@CNT composites with unique dendritic core–shell structure can provide abundant and easily accessible redox-active sites, which contribute to improve diffusion rate of lithium ions and the corresponding specific capacity. This synergistic structural design enables excellent electrochemical performance of the cathodes, giving rise to 95% utilization of redox-active sites, high rate capability (81% capacity retention at 10 C), and long cycling stability (86% retention after 600 cycles at 5 C). As the first example to explore the application of 1D COFs in the field of energy storage, this study demonstrates the great potential of this novel type of linear crystalline porous polymers in battery technologies.     

Current Distributions in Quantum Hall Effect Devices

This paper addresses the question of how current is distributed within quantum Hall effect devices. Three types of flow patterns most often mentioned in the literature are considered. They are: (1) skipping orbits along the device periphery (which arise from elastic collisions off hard-walled potentials); (2) narrow conducting channels along the device sides (which are presumed to be generated from confining potentials); and (3) currents distributed throughout the device (which are assumed to arise from a combination of confining and charge-redistribution potentials). The major conclusions are that skipping orbits do not occur in quantum Hall effect devices, and that nearly all of the externally applied current is located within the device interior rather than along the device edges.     

The Infrared Hall Effect in YBCO: Temperature and Frequency Dependence of Hall Scattering

We measure the Hall angle, _H , in YBCO films in the far- and mid-infrared to determine the temperature and frequency dependence of the Hall scattering. Using novel modulation techniques we measure both the Faraday rotation and ellipticity induced by these films in high magnetic fields to deduce the complex conductivity tensor. We observe a strong temperature dependence of the mid-infrared Hall conductivity in sharp contrast to the weak dependence of the longitudinal conductivity. By fitting the frequency dependent normal state Hall angle to a Lorentzian _H () = _H /( _H – i) we find the Hall frequency, _H , is nearly independent of temperature. The Hall scattering rate, _H , is consistent with _H T ² up to 200 K and is remarkably independent of IR frequency suggesting non-Fermi liquid behavior.     

孔底准真空间隔装药的爆破效果试验研究

采用相似模拟试验对孔底准真空间隔装药的爆破效果进行研究。通过高速应变测试、爆破振动测试、爆破漏斗容积测量及块度测量分析爆破效果。相同实验条件下对比水、空气、准真空三种间隔装药方式:准真空所测得的平均峰值最小为1.67με;准真空间隔装药方式爆破引起的爆破震动速度峰值小于空气间隔及水间隔;空气间隔与准真空间隔装药方式爆破后,均能获得比连续装药方式更大的漏斗体积;准真空间隔装药方式爆破时爆出的块度大小集中在块度半径R为10~12.5 mm之间,块度均匀性较其他间隔装药方式好。得到以下结论:孔底准真空间隔装置的使用能延长爆破作用时间,增大爆破漏斗体积,减少大块率且准真空层与埋药深度之比在37.5%~50%范围内,爆破能量利用率大。