各向异性层状强关联金属中沿c轴方向的电荷输运

对于欠掺杂铜氧化物超导体 ,当温度Ｔ高于超导转变温度Ｔｃ 但低于赝能隙温度Ｔ 时 ,便有正常态赝能隙打开 (在ａｂ平面布里渊区的角隅位置 ) .赝能隙的存在对ｃ轴方向的电荷输运起阻碍作用 ,结果导致正常态输运行为的强二维性 ,即电阻率ρａｂ(Ｔ)的金属行为和 ρｃ(Ｔ)的绝缘体行为 .当温度降至Ｔｃ 以下 ,层间的约瑟夫森耦合使得材料转变为三维各向同性超导态 .其中有效维数的转变一直是凝聚态物理的一个热点课题 .上述维数转变的问题也存在于非超导的层状强关联金属中 ,例如 (Ｂｉ0 5Ｐｂ0 5) 2 Ｂａ3 Ｃｏ2 Ｏｙ(简称ＢＰＢ ＣＯ ,它…     

Asymmetric Tunneling Conductance and the Non-Fermi Liquid Behavior of Strongly Correlated Fermi Systems

Tunneling differential conductivity (or resistivity) is a sensitive tool to experimentally test the non-Fermi liquid behavior of strongly correlated Fermi systems. In the case of common metals the Landau–Fermi liquid theory demonstrates that the differential conductivity is a symmetric function of bias voltage V. This is because the particle–hole symmetry is conserved in the Landau–Fermi liquid state. When a strongly correlated Fermi system turns out to be near the topological fermion condensation quantum phase transition, its Landau–Fermi liquid properties disappear so that the particle–hole symmetry breaks making the differential tunneling conductivity to be asymmetric function of V. This asymmetry can be observed when a strongly correlated metal is in its normal, superconducting or pseudogap states. We show that the asymmetric part of the dynamic conductance does not depend on temperature provided that the metal is in its superconducting or pseudogap states. In normal state, the asymmetric part diminishes at rising temperatures. Under the application of magnetic field the metal transits to the Landau–Fermi liquid state and the differential tunneling conductivity becomes a symmetric function of V. These findings are in good agreement with recent experimental observations.     

三元杂多阴离子层状化合物的合成、表征及催化活性

用离子交换法合成了具有Keggin结构的三元杂多阴离子层状化合物LDH-K8[MnCu(H2O)W11O39],LDH-K8[MnFe(H2O)W11O39],LDH-K8[MnCo(H2O)W11O39]和LDH-K8[MnZn(H2O)W11O39],并用XRD、IR、UV对其进行了表征。结果表明:杂多阴离子进入水滑石层间后,仍保留了其Keggin结构。利用层状化合物催化合成乙酸正丁酯考察其催化活性,结果表明:层状化合物在酯化反应中显示优良的催化性能。     

11-钨锌三元杂多阴离子层状化合物的合成、表征及催化活性

用离子交换法将具有K egg in结构11-钨锌三元杂多化合物K8[M ZnW11（H2O）O39]（M=Co2＋、N i2＋、Cu2＋、Cd2＋）嵌入到Zn2A l类水滑石中,得到层状化合物：Zn2A l-[M ZnW11（H2O）O39]（M=Co2＋、N i2＋、Cu2＋、Cd2＋）,并用XRD、IR、UV对其进行了表征。结果表明,杂多阴离子进入水滑石层间后,仍保留了其K egg in结构。利用层状化合物催化合成乙酸正丁酯考察其催化活性,结果表明,层状化合物在酯化反应中显示优良的催化性能。     

Laplace Sequences of Surfaces in Projective Space and Two-Dimensional Toda Equations

We find that the Laplace sequences of surfaces of period n in projective space P _n–1 have two types, while type II occurs only for even n. The integrability condition of the fundamental equations of these two types have the same form

Fermi Arcs and DC Transport in Nanowires of Dirac and Weyl Semimetals

The transport properties and electron states in cylinder nanowires of Dirac and Weyl semimetals are studied paying special attention to the structure and properties of the surface Fermi arcs. The latter make the electric charge and current density distributions in nanowires strongly nonuniform as the majority of the charge density is accumulated at the surface. It is found that a Weyl semimetal wire also supports a magnetization current localized mainly at the surface because of the Fermi arcs contribution. By using the Kubo linear response approach, the direct current (DC) conductivity is calculated and it is found that its spatial profile is nontrivial. By explicitly separating the contributions of the surface and bulk states, it is shown that when the electric chemical potential and/or the radius of the wire is small, the electron transport is determined primarily by the Fermi arcs and the electrical conductivity is much higher at the surface than in the bulk. Due to the rise of the surface-bulk transition rate, the relative contribution of the surface states to the total conductivity gradually diminishes as the chemical potential increases. In addition, the DC conductivity at the surface demonstrates noticeable peaks when the Fermi level crosses energies of the surface states.     

Nucleation,Growth, and Aggregation of Au Nanocrystals on Liquid Surfaces

We report the formation of gold ramified aggregates after deposition of Au on an ionic liquid surface by thermal evaporation method at room temperature.It is observed that the aggregates are composed of both granules and nanocrystals with hexagonal or triangular appearances.The most probable size of the nanocrystals is much larger than that of the granules and it increases with the nominal deposition thickness.The formation mechanism of the granules,nanocrystals and aggregates is presented.     

Anisotropic resistivity of the monolayer graphene in the trigonal warping and connected Fermi curve regimes

In the present study, the anisotropic resistivity of the monolayer graphene has been obtained in semiclassical regime beyond the Dirac point approximation. In particular, detailed investigations were made on the dependence of conductivity on the Fermi energy. At low energies, in the vicinity of the Dirac points, band energy of the monolayer graphene is isotropic at the Fermi level. Meanwhile, at the intermediate Fermi energies anisotropic effects such as trigonal warping is expected to be the origin of the anisotropic resistivity. However, besides the band anisotropy there also exists an other source of anisotropic resistivity which was introduced by scattering matrix. At high energies it was shown that the band anisotropy is less effective than the anisotropy generated by the scattering matrix. It was also shown that there exist two distinct regimes of anisotropic resistivity corresponding the trigonal warping and connected Fermi curve at intermediate and high energies respectively.     

One-Step Nanosecond-Laser Microstructuring,Sulfur-Hyperdoping,and Annealing of Silicon Surfaces in Liquid Carbon Disulfide

We perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that singlestep microstructuring and deep (up to 2–3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (10⁴ cm^?1) spectrally flat near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin-film silicon photovoltaic devices.     

Reconstructions of the Electron Dynamics in Magnetic Field and the Geometry of Complex Fermi Surfaces

Journal of Experimental and Theoretical Physics - The paper considers the semiclassical dynamics of electrons on complex Fermi surfaces in the presence of strong magnetic fields. The...     

Topological Aspect and Bifurcation of Disclination Lines in Two—Dimensional Liquid Crystals

Using φ-mapping method and topological current theory,the topological structure and bifurcation of disclination lines in two-dimensional liquid crystals are studied.By introducing the strength density and the topological current of many disclination lines,the total disclination strength is topologically quantized by the Hopf indices and Brouwer degrees at the singularities of the director field when the Jacobian determinant of director field does not vanish.When the Jacobian determinant vanishes,the origin,annihilation and bifurcation processes of disclination lines are studied in the neighborhoods of the limit points and bifurcation points,respectively.The branch solutions at the limit point and the different directions of all branch curves at the bifurcation point are calculated with the conservation law of the topological quantum numbers.It is pointed out that a disclination line with a higher strength is unstable and it will evolve to the lower strength state through the bifurcation process.     

三元层状陶瓷M-Al-N(M=Ti,Zr,Hf)的结构及力学性质的第一性原理模拟

基于第一性原理方法,探索M-Al-N（M=Ti,Zr,Hf）结构的稳定性,计算其力学性质.计算M-Al-N化合物的能量,发现除实验已知的结构Ti₂AlN和Ti₄AlN₃、Zr₂AlN、Hf₂AlN外,还存在两种新的热力学稳定结构Zr₄AlN₃、Hf₄AlN₃.弹性常数和声子谱的计算,表明这两个结构是力学稳定和晶格动力学稳定的.计算M₂AlN和M₄AlN₃的力学性质,发现它们具有高的体模量、剪切模量、弹性模量、维氏硬度等;分析其力学性质随组分比例、组成元素的变化规律,为该类材料的选择和应用提供理论依据.最后计算M₂AlN和M₄AlN₃的电子态密度和分态密度、电子密度分布、Mulliken群分析等.     

Generating Functional in CFT and Effective Action for Two-Dimensional Quantum Gravity on Higher Genus Riemann Surfaces

We formulate and solve the analog of the universal Conformal Ward Identity for the stress-energy tensor on a compact Riemann surface of genus g > 1, and present a rigorous invariant formulation of the chiral sector in the induced two-dimensional gravity on higher genus Riemann surfaces. Our construction of the action functional uses various double complexes naturally associated with a Riemann surface, with computations that are quite similar to descent calculations in BRST cohomology theory. We also provide an interpretation of the action functional in terms of the geometry of different fiber spaces over the Teichmüller space of compact Riemann surfaces of genus g > 1. Received: 12 September 1996 / Accepted: 6 January 1997     

Nonequilibrium Electrical,Thermal and Spin Transport in Open Quantum Systems of Topological Superconductors,Semiconductors and Metals

Journal of Statistical Physics -     

Anisotropic Transport on Monolayer and Multilayer Phosphorene in the Presence of an Electric Field

We demonstrate theoretically the anisotropic quantum transport of electrons through an electric field on monolayer and multilayer phosphorene. Using the long-wavelength Hamiltonian with continuum approximation, we find that the transmission probability for transport through an electric field is an oscillating function of incident angle, electric field intensity, as well as the incident energy of electrons. By tuning the electric field intensity and incident angle, the channels can be transited from opaque to transparent. The conductance through the quantum waveguides depends sensitively on the transport direction because of the anisotropic effective mass, and the anisotropy of the conductance can be tuned by the electric field intensity and the number of layers. These behaviors provide us an efficient way to control the transport of phosphorene-based microstructures.     

Asphericity in the Fermi Surface and Fermi Energy of Na-K, Na-Rb and Na-Cs Binary Alloys

Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior ofthe K, Rb, and Cs with the Na generates the Fermi surface distortion (FSD) of bce simple metals. The FS of Na-K,Na-Rb, and Na-Cs solid solution is a distorted sphere with the largest deviation along [110]. We have found that theimpact of local-field correction function on FSD is maximun at [100] point and minimum at [111] point. The exchangeand correlation effect is found to suppress the value of FE.