Modified Transition Temperature Equation for Superconductors

We present the replacement and modification of the Debye temperature θD by the average phonon frequency （ω） in the Rowell [Solid State Commun. 19 （1976） 1131] linear transition-temperature equation for superconducting materials. We not only improve Rowell＇s results but also describe the experimental results accurately and consistently for the various superconducting systems which cover the entire range of λ between 0.72 and 2.59. The proposed linear equation of the transition temperature Tc is found to be better and more accurate than those of dain and Kachhava [Can. d. Phys. 58 （1980） 1614].     

手征对称性动力学破缺和铜氧化物超导体相变的三维量子电动力学研究

利用三维量子电动力学理论中的Dyson-Schwinger方程方法, 研究了零温情况下平面铜氧化合物超导体的反铁磁相和d波超导相之间的相变. 通过在朗道规范下近似解析求解和数值求解完全耦合的Dyson-Schwinger方程、并将所得结果与1/N展开方法的结果相比较, 发现在半填充准费密子味道数约小于等于4的情况下, 通过手征对称性自发破缺, d波超导相可以演化到反铁磁相, 并且反铁磁相有可能与d波超导相共存. 通过进一步比较不同相的压强, 还说明反铁磁与d波超导共存相为稳定相, 从而反铁磁相确实可以与d波超导相共存.     

Pressure Effects on Anisotropic Low-Dimensional Superconductors Close to an Electronic Topological Transition

Hydrostatic pressure or anisotropic stress can modify the electronic properties of a metal, thus inducing a change in the topology of its Fermi surface. In the case of low-dimensional anisotropic superconductors (such as high- T c cuprates, some organic salts, or heavy Fermion compounds), such changes result in a nonmonotonic dependence of several properties on the critical parameter z , measuring the distance of the chemical potential from the electronic topological transition (ETT). This has to be contrasted with the monotonic, nearly step-like z -dependence of the same quantities in the 3D case. Such a non-monotonic behavior is in agreement with the trend observed for T c as a function of pressure and other material specific quantities in several high- T c cuprate compounds. On the other hand, higher pressures than those reported in the literature (～ 10 kbar) should be investigated, in order to find evidence for ETT effects in the BEDT-TTF-based salts.     

Delocalization in Random Polymer Models

 A random polymer model is a one-dimensional Jacobi matrix randomly composed of two finite building blocks. If the two associated transfer matrices commute, the corresponding energy is called critical. Such critical energies appear in physical models, an example being the widely studied random dimer model. It is proven that the Lyapunov exponent vanishes quadratically at a generic critical energy and that the density of states is positive there. Large deviation estimates around these asymptotics allow to prove optimal lower bounds on quantum transport, showing that it is almost surely overdiffusive even though the models are known to have pure-point spectrum with exponentially localized eigenstates for almost every configuration of the polymers. Furthermore, the level spacing is shown to be regular at the critical energy. Received: 2 January 2002 / Accepted: 10 September 2002 Published online: 19 December 2002     

Delocalization transition in one dimension

Singular extended states among random system localized states are proved to be a general rule. When a Fermi energy coincides with the extended state energy, a residual resistance becomes proportional to the square of the system length.     

Dynamical Chiral Symmetry Breaking and Phase Transition of Cuprate Superconductors in QED3

With the coupled Dyson-Schwinger equations in the framework of the unified QED₃ theory, we study the phase transition between the antiferromagnet(AF) and the d-wave superconductor (dSC) of planar cuprates at T=0. By solving the coupled Dyson-Schwinger equations both analytically and numerically in rainbow approximation in Landau gauge and comparing the obtained results with that given in the 1/N expansion, we find that there exists a chiral symmetry breaking from dSC phase to AF phase when the quasi-fermion flavors N≤4 in half-filling and the AF phase can possibly coexist with the dSC phase in the underdoped region. By comparing the pressure between the coexistent AF-dSC phase and dSC phase, we find that AF-dSC coexisting phase is the stable phase, the AF phase can then coexist with the dSC phase.     

Combustion Wave Stability in Transition through the Interface of Gasless Systems

In this paper, using mathematical modeling, we study combustion wave stability in transition through the interface of gasless systems. The effect of a gas layer separating two chemically active gasless layers on the combustion wave stability was studied at all stages of the transition. Using the criteria obtained, we estimate the stability conditions of the transition combustion wave. The nonstationary dynamics of the combustion wave transition through the gas gap is studied with allowance for competing mechanisms of heat transfer, such as conductive and radiant transfer. We analyze the effect of radiation heat transfer in the gas gap on the characteristics and stability of the transient combustion process. The failure region of the igniter combustion wave is determined through the approach to the ignition system, while estimates of temperature and heat flux at the interface of the systems are given with respect to the time of the igniter combustion completion under conditions of dominant conductive and radiant heat transfer.     

Delocalization and Heisenberg's uncertainty relation

In the one-dimensional Anderson model the eigenstates are localized for arbitrarily small amounts of disorder. In contrast, the Aubry-André model with its quasiperiodic potential shows a transition from extended to localized states. The difference between the two models becomes particularly apparent in phase space where Heisenberg's uncertainty relation imposes a finite resolution. Our analysis points to the relevance of the coupling between momentum eigenstates at weak potential strength for the delocalization of a quantum particle. Received 3 May 2002 / Received in final form 2 October 2002 Published online 29 November 2002     

Instabilities in Technical Superconductors

Physics of Atomic Nuclei - Characteristic regularities of development of thermoelectrodynamic processes in current-carrying elements of superconducting magnet systems are discussed. It is shown...     

Superconductor-Metal Quantum Transition at the EuO/KTaO_3 Interface

We report the experimental investigation of the superconductor-metal quantum phase transition of the Eu O/KT_a O₃ interface. Around the transition, a divergence of the dynamical critical exponent is observed, which supports the quantum Griffiths singularity in the Eu O/KT_a O₃ interface. The quantum Griffiths singularity could be attributed to large rare superconducting regions and quenched disorders at the interface. Our results could pave the way for s...     

Bianchi Type-I String Cosmological Model in Creation-Field

Hoyle-Narlikar C-field has been introduced to study cosmic strings in Bianchi type-I space-time. The solutions have been studied when the creation field C is a function of time t only. The geometrical and physical aspects for the models have also been studied.     

Piezomagnetism in Ferromagnetic Superconductors

Journal of Experimental and Theoretical Physics - The appearance of magnetization during the application of mechanical stress and the creation of elastic deformation during the application of a...     

Superconductors in gravitational field

The classical London equations in a covariant form hold for superconductors in a curved space-time. Gravity effects of superconducting bodies at 0 K are discussed.     

Viscous Fluid Cosmology in Bianchi Type-I Space-Time

The paper presents a spatially homogeneous and anisotropic Bianchi type-I cosmological model consisting of a dissipative fluid. The field equations are solved explicitly by using a law of variation for mean Hubble parameter, which is related to average scale factor and yields a constant value for deceleration parameter. We find that the constant value of deceleration parameter describes the different phases of the evolution of universe. A barotropic equation of state (p=γ ρ) together with a linear relation between shear viscosity and expansion scalar, is assumed. It is found that the viscosity plays a key role in the process of the isotropization of the universe. The presence of viscous term does not change the fundamental nature of initial singularity. The thermodynamical properties of the solutions are studied and the entropy distribution is also given explicitly.