Pairing of Cooper pairs in a fully frustrated Josephson-junction chain

We study a one-dimensional Josephson-junction chain embedded in a magnetic field. We show that, when the magnetic flux per elementary loop equals half the superconducting flux quantum phi0 = h/2e, a local Z2 symmetry arises. This symmetry is responsible for a nematic Luttinger liquid state associated with bound states of Cooper pairs. We analyze the phase diagram and discuss some experimental possibilities to observe this exotic phase.     

Gap Caused by Strong Pairing in the Ladder Model of DNA Molecules

By directly diagonalizing the Hamiltonian of the ladder model of deoxyribonucleic acid （DNA） molecules, the density of states is obtained. It is found that DNA behaves as a conductor when the interchain hopping is smaller than twice the intrachain one, otherwise, DNA behaves as a semiconductor.     

Dimension Effects in Insulating NbTiN Disordered Films and the Asymptotic Freedom of Cooper Pairs

JETP Letters - We investigate the evolution of the electronic transport in disordered NbTiN films at the insulating side of the superconductor-insulator transition as function of the effective...     

中心对称萘酞菁分子二次谐波产生的实验研究

研究了三种萘酞菁化合物LB膜的制备,并通过二次谐波产生的方法研究了单个对称取代的萘酞菁化合物及双(四叔丁基萘酞菁)铒的二阶非线性光学特性,并对它们的产生机理进行了简单的讨论.单个对称取代的萘酞菁化合物,它们的二次谐波产生机制为磁偶极子耦合机制,双(四叔丁基萘酞菁)铒的二阶非线性光学特性起源于电四极子模型,且它的二阶非线性极化率χ(2)(或超极化率β)大于单个萘酞菁化合物.     

非传统超导PuCoGa5晶体结构和电子性质的密度泛函理论研究

基于密度泛函理论的全势能线性缀加平面波方法（FLAPW）,采用局域自旋密度近似（LSDA）及LSDA+U方法报道了Pu基超导体系PuCoGa₅的晶格参数,原子占位和电子性质.LSDA+U方法不仅考虑Pu-5f而且考虑了Co-3d的库伦排斥作用U和Hund交换相关作用J.结果表明LSDA+U在同时考虑Pu和Co的强关联作用时晶格参数和原子占位与相关理论和实验数据吻合较好,特别是PuCoGa₅中Pu-5f的强定域特征尤其是自旋向下的电子.此外,Pu-5f与Co-3d电子的轨道杂化明显强于Ga-4p电子.     

Pairing in multiparticle amplitudes: Inclusive distributions

A model for multi-pion production in the central region in high-energy collisions is studied which describes factorizable emission of pion pairs. A mathematical identification between the exclusive cross section for pion emission in our model (with all interference terms) and the configurational probability distribution function for a classical system of interacting molecules in equilibrium is exploited to obtain an expansion for the asymptotic single-particle inclusive distribution, the two-particle inclusive correlation function, and the exponent of s in the total cross section by means of cluster diagrams. An integral equation is exhibited for summing the terms corresponding to the cluster diagrams.A specific model is then considered, which we call “s-channel pole dominance”. In this model the amplitude is assumed to be large only when the subenergies of pairs of pions are near the mass of a low-lying two-pion resonance, and the transverse momentum of each resonance is small. The dependence of the amplitude on other variables is ignored, so that we effectively have independent emission of two-pion resonances with non-zero width. It is seen that an I = 0 or I = 1 resonance results in a positive two-particle inclusive I = 2 correlation function at small rapidity separations, as s → ∞, and that the correlation function can have an exponential “tail” in rapidity of qualitatively longer range than the resonance. A crude numerical simulation of a broad I = 0 spinless resonance is discussed, and the resulting I = 2 inclusive correlation function is seen to be quite large at small rapidity separations, and to have the same exponential “tail” as the I = 0 correlation function.     

线型分子势能函数及第二维里系数计算

本文以两中心的Lennard—Jones（2CLJ）流体为研究对象,通过引入与温度相关的势能参数,提出了改进型的2CLJDQP势能函数模型。应用此模型计算了乙烷（C2H6）、六氟乙烷（C2F6）、氟甲烷（CH3F）、氯甲烷（CH3C1）、1,1,1-三氟乙烷（CH3CF3）、二氟乙烷（CH3CHF2）的第二维里系数,较...     

含偶氮分子的ormocer固体薄膜制备及二阶光学非线性

利用溶胶－凝胶（sol-gel)低温合成非晶态技术,以γ－氨基丙基三乙氧基硅烷（3-aminopropyl triethoxysilane,KH550)与γ－缩水甘油醚基丙基三甲氧基硅烷（3－glycidoxy-propltrimethoxysilane,KH560)为先驱体,把Disperse Orange3(DO3)偶氮分子以3wt%的浓度掺杂到上述溶胶与ormocer(organic modified ceramic)体系中,在ITO片上制备成厚度为4μm的DO3／90KH560－10KH550薄膜。经高温电晕极化后,用二次谐波发生装置,测量出薄膜材料的二次谐波强度,并计算出经极化后薄膜材料的p→p的二阶有效极化系数deff=0.11pm/V。极化24小时后,其SHG强度基本保持不变,大约为刚极化后的80％大小,我们认为这主要是由于介质中KH550的引入,其中－NH2基团与DO3中的－NH2之间形成了氢键的作用,以及由氢键引起的介质材料进一步致密化作用,使得DO3分子不易发生弛豫作用,而保持极化后的分子状态。     

Pairing symmetries in cuprates: A Gorkov formalism

Inspite of the direct evidence for Cooper pairing in the cuprates as in conventional superconductors, the pairing symmetry in the cuprate superconductors is still considered to be a controversial and a highly debatable topic. The microscopic equations appropriate for these new materials, essentially the yttrium based compounds, are discussed following Gorkov's formalism for the conventional superconductors. Various types of symmetry of the pairing parameter are considered. In this study we consider the anisotropic nature of the gap parameter to write the mean-field equations of the cuprates. We observe that the symmetry of the potential is fundamental in deciding the nature of the anisotropy in the gap parameter.     

Gapless magnetic and quasiparticle excitations due to the coexistence of antiferromagnetism and superconductivity in CeRhIn5: a study of 115In NQR under pressure

We report systematic measurements of ac susceptibility, nuclear-quadrupole-resonance spectrum, and nuclear-spin-lattice-relaxation time (T1) on the pressure (P)-induced heavy-fermion superconductor CeRhIn5. The temperature (T) dependence of 1/T(1) at P=1.6 GPa has revealed that antiferromagnetism (AFM) and superconductivity (SC) coexist microscopically, exhibiting the respective transition at T(N)=2.8 K and T(MF)(c)=0.9 K. It is demonstrated that SC does not yield any trace of gap opening in low-lying excitations below T(onset)(c)=2 K, but T(MF)(c)=0.9 K, followed by a T(1)T=const law. These results point to the unconventional characteristics of SC coexisting with AFM. We highlight that both of the results deserve theoretical work on the gapless nature in the low-lying excitation spectrum due to the coexistence of AFM and SC and the lack of the mean-field regime below T(onset)(c)=2 K.     

Gapless Fermi surfaces of anisotropic multiband superconductors in a magnetic field

We propose that a new state with a fully gapless Fermi surface appears in quasi-2D multiband superconductors in magnetic field applied parallel to the plane. It is characterized by a paramagnetic moment caused by a finite density of states on the open Fermi surface. We calculate thermodynamic and magnetic properties of the gapless state for both s-wave and d-wave cases, and discuss the details of the first order metamagnetic phase transition that accompanies the appearance of the new phase in s-wave superconductors. We suggest possible experiments to detect this state both in the s-wave (2-H NbSe2) and d-wave (CeCoIn5) superconductors.     

Effect of the Electron-Vibrational Interaction on the Second Electron Transition of Tetraazaporphin and Tetraazachlorin Molecules

We have traced the change in the complex structure of the intense 0–0 band of the electronic S ₂ S ₀ transition in the quasi-line absorption spectra (n-octane, 77 K) for individual types of impurity centers in the series of compounds tetraazaporphin–tetraazachlorin–di(tert-butylbenzo)barrelene-substituted tetraazachlorin. It has been concluded that the reason for the appearance of this structure is the interaction of the pure electronic S ₂ state with the vibronic S ₁ states rather than the Franck–Condon manifestation of low-frequency vibrations. Attempts to detect the short-wave S ₂ S ₀ fluorescence for all three compounds were unsuccessful. The reasons for the difference from the case of bacteriochlorin, in which such a fluorescence was observed earlier, are discussed.     

Gapless excitations of axially symmetric vortices in systems with tensorial order parameter

We extend the results of previous work on vortices in systems with tensorial order parameters. Specifically, we focus our attention on systems with a Ginzburg–Landau free energy with a global U(1)_P×SO(3)_S×SO(3)_L$U{\left(1\right)}_P\times SO{\left(3\right)}_S\times SO{\left(3\right)}_L$ symmetry in the phase, spin and orbital degrees of freedom. We consider axially symmetric vortices appearing on the spin–orbit locked SO(3)_S+L$SO{\left(3\right)}_{S+L}$ vacuum. We determine the conditions required on the Ginzburg–Landau parameters to allow for an axially symmetric vortex with off diagonal elements in the order parameter to appear. The collective coordinates of the axial symmetric vortices are determined. These collective coordinates are then quantized using the time dependent Ginzburg–Landau free energy to determine the number of gapless modes propagating along the vortex.     

全内反射构型下分子在十六烷-水界面取向角度的二次谐波测量

测量了在全内反射条件及非全内反射条件下,两种探针分子在十六烷-水界面上的取向角度.通过详细的偏振分析,发现探针分子在两种构型下的取向角度测量结果一致.表明全内反射条件下,取向角度的测量和偏振分析同样是准确且可行的.     

Cosmic chemistry: Molecules in space

Molecular clouds contain most of the mass of gas in interstellar space and are the source of matter from which new stars are formed. The clouds can be studied by means of the radio emission in rotational transitions of the molecules that they contain. We describe the chemical routes by which these molecules are formed, and their ultimate incorporation into icy mantles frozen onto dust grains. The role that chemistry plays in tracing and controlling processes in star-forming regions and in near-stellar environments is briefly indicated.     

Symmetrization of Wave Functions of 4- and 5-Atom Molecules

Symmetrized wave functions of 4- and 5-atom molecules with two, three, or four identical atoms are constructed in general form. The symmetrization of the angular and radial parts of the vibrational-rotational wave function is examined in detail. The representation matrix and the Clebsch-Gordan coefficients of the permutation group S _n (n = 3, 4) are adapted for the use in molecular spectroscopy. This makes it easier to draw analogies with the theory of effective Hamiltonian. The use of symmetrized wave functions is shown to significantly alleviate the problem of calculating the vibrational-rotational energy levels from the potential energy surface for such molecules as CH₄, CH₃D, CH₃Cl, etc.     

Pairing symmetry and pairing state in ferropnictides: Theoretical overview

We review the main ingredients for an unconventional pairing state in the ferropnictides, with particular emphasis on interband pairing due to magnetic fluctuations. Summarizing the key experimental prerequisites for such pairing, the electronic structure and nature of magnetic excitations, we discuss the properties of the s^± state that emerges as a likely candidate pairing state for these materials and survey experimental evidence in favor of and against this novel state of matter.     

第二代高温超导长带传输临界电流表征及其对电压引线间距的依赖性

传输法(或四引线法)测量可直观、准确的体现超导材料临界电流特性.为表征第二代高温超导长带临界电流及其沿长度方向均匀性特征,本文以四引线法为基础,建立了动态传输法测量装置,并对该装置的重复稳定性进行了评估,同时,表征了第二代高温超导长带临界电流对电压引线间距的依赖关系.实验结果发现,重复性测量不确定度为0.74%(<1%),该装置具有良好重复稳定性,且测量速度达200～300 m/h,满足高温超导产业化测量需求;随着电压引线间距增加,第二代高温超导长带各测试段临界电流的最大值和最小值分别呈现逐渐减小和增加的趋势,平均值变化不大,保持稳定,其中最大值和最小值向平均值收敛;各测试段临界电流的标准偏差随电压引线间距的增加而减小,通过线性拟合得,标准偏差与电压引线间距关系为:s=3.47/L₂^0.36.传输法测量装置的建立及其关键参数电压引线间距对临界电流表征的影响研究,对推动第二代高温超导产业化进程具有重大意义.