非晶材料与物理近期研究进展

由于结合了金属和玻璃的特性,非晶合金表现出许多新奇和优异的力学和物理性质,在很多领域具有广泛的应用前景.非晶合金具有连续可调的成分、简单无序的原子结构、丰富多变的材料性质,为研究非晶态物理中的许多共性科学问题提供了理想的模型材料.块体非晶合金的发展更是将玻璃和液体及其相关科学问题的研究推进到凝聚态物理和材料科学的研究前沿.中国科学院物理研究所极端条件物理重点实验室亚稳材料合成、结构及性能研究组(EX4组)近二十年来一直致力于非晶材料和物理的研究,在新型非晶合金的制备、物性以及相关机理的研究上取得了许多重要成果.本文介绍团队最近在非晶材料和物理机理方面取得的研究成果,包括非晶合金的动力学行为和调控、非晶合金的表面动力学、功能应用以及材料探索新方法等.     

Self-organization of directed networks through asymmetric coupling

In this Letter, self-organization of directed networks is surveyed. Inspired from the results in neural networks research, we propose an asymmetric coupling scheme with simple edge deleting rules. Results show that all-to-all networks can be organized into scale-free networks with feed-forward structures. Corresponding analysis is also given.     

Self-organization of neural networks: Noise-induced transition

A model for the formation and plastic behaviour of ordered neural mapping is given. A self-organizing mechanism is presented in terms of activity dependent modifiable synapses. The establishment of the “order” is in accordance with the spirit of the theory of “noise-induced transitions”.     

Fast-ion conduction and flexibility of glassy networks

We observe two thresholds in the variations of electrical conductivity of dry (AgI)_{x}(AgPO3)_{1-x} solid electrolyte glasses, when the AgI additive concentration x increases to 9.5% and to 37.8%. Raman scattering complemented by calorimetric measurements confirms that these thresholds are signatures of the rigidity phase transitions at x=9.5% from a stressed rigid to an isostatically (stress-free) rigid phase, and at x=37.8% from isostatically rigid to a flexible phase. In the flexible phase, the electrical conductivity seems to increase as a power of x. This is in good agreement with the theoretical prediction based on 3D percolation.     

Self-organization of structures and networks from merging and small-scale fluctuations

We discuss merging-and-creation as a self-organizing process for scale-free topologies in networks. Three power-law classes characterized by the power-law exponents , 2 and are identified and the process is generalized to networks. In the network context the merging can be viewed as a consequence of optimization related to more efficient signaling.     

Self-organization of a critical state on complex networks

The critical dynamics of a two-threshold system with the law of conservation of the basic quantity z and in the absence of sink on a scale-free network has been studied. It has been shown that the critical state that is a set of metastable states appears in such a system. The structure of the metastable states is a set of stable clusters of nodes at which the z values are close to the positive and negative threshold values. Avalanches transforming the system from one metastable state to another state appear in the system. The absence of sink is effectively replaced by the annihilation process. The statistics of avalanches in such a system has been analyzed. It has been shown that the self-organized critical state can appear in the system.     

Progress in the physics of complex networks

Current research investigating the thermo-mechanical behavior of materials at elevated and high loading conditions is performed on two major branches: one is concerned with the elastic, plastic and failure behavior of materials described by constitutive relations in the deviatoric stress space. The other branch is focused on the shock wave formation and propagation where the hydrostatic stress represented by an Equation of State is of primary interest.     

张量网络与神经网络在物理学中的应用和交融

基于张量网络的数值重正化群方法,被广泛地应用到物理学的研究中,已经成为量子多体计算方法大家庭的重要一员。近年来,基于神经网络的机器学习方法也逐渐渗透到物理学领域,并被成功应用在量子多体等问题的研究中。文章简要综述了近年来张量网络和神经网络在凝聚态物理和统计物理学的应用,并讨论了两者的相互交叉和结合。     

Self-organization of balanced nodes in random networks with transportation bandwidths

We apply statistical physics to study the task of resource allocation in random networks with limited bandwidths along the transportation links. The mean-field approach is applicable when the connectivity is sufficiently high. It allows us to derive the resource shortage of a node as a well-defined function of its capacity. For networks with uniformly high connectivity, an efficient profile of the allocated resources is obtained, which exhibits features similar to the Maxwell construction. These results have good agreements with simulations, where nodes self-organize to balance their shortages, forming extensive clusters of nodes interconnected by unsaturated links. The deviations from the mean-field analyses show that nodes are likely to be rich in the locality of gifted neighbors. In scale-free networks, hubs make sacrifice for enhanced balancing of nodes with low connectivity.     

The physics of communicability in complex networks

A fundamental problem in the study of complex networks is to provide quantitative measures of correlation and information flow between different parts of a system. To this end, several notions of communicability have been introduced and applied to a wide variety of real-world networks in recent years. Several such communicability functions are reviewed in this paper. It is emphasized that communication and correlation in networks can take place through many more routes than the shortest paths, a fact that may not have been sufficiently appreciated in previously proposed correlation measures. In contrast to these, the communicability measures reviewed in this paper are defined by taking into account all possible routes between two nodes, assigning smaller weights to longer ones. This point of view naturally leads to the definition of communicability in terms of matrix functions, such as the exponential, resolvent, and hyperbolic functions, in which the matrix argument is either the adjacency matrix or the graph Laplacian associated with the network.     

中国和国际物理教育合作网的比较与分析

教育期刊论文的情况往往是教学情况的一种真实反映。中国、美国和英国的主要物理教育期刊刊名分别为《物理教学》、《大学物理》、The Physics Teacher、American Journal of Physics和Physics Education，文章基于这五个物理教育期刊的相关参数分别建立相应的物理教育合作网，从论文作者数目及不同论文作者间的合作关系的角度，揭示了中国与国际物理教育研究的差距，并为它们的进一步发展提供了启发性和指导性建议。     

Self-organization and the formation of helicoidal polymer structures

The self-organization of three-dimensional anharmonic chains of atoms with strong interactions between nearest-neighbor atoms and various types of weak interactions between non-nearest neighbors is investigated by the method of molecular dynamics. It is observed that in all cases short helical segments form initially, causing the molecule either to evolve into a stable helicoidal structure or to collapse into a globule. It is shown that the stability of the helicoidal structure is caused by correlations among the weak interactions. Fiz. Tverd. Tela (St. Petersburg) 39, 1883–1888 (October 1997)     

Self-organization and the dynamical nature of ventricular fibrillation

This article reviews recent data supporting the conjecture that, in the structurally and electrophysiologically normal heart, cardiac fibrillation is not a totally random phenomenon. Experimental and numerical studies based on the theory of excitable media suggest that fibrillation in the mammalian ventricles is the result of self-organized three-dimensional (3-D) electrical rotors giving rise to scroll waves that move continuously (i.e., drift) throughout the heart at varying speeds. A brief review of studies on the dynamics of rotors in two-dimensional (2-D) and 3-D excitable media is presented with emphasis on the experimental demonstration of such dynamics in cardiac muscle of various species. The discussion is centered on rotor dynamics in the presence and the absence of structural heterogeneities, and in the phenomena of drifting and anchoring, which in the electrocardiogram (ECG) may manifest as life-threatening cardiac rhythm disturbances. For instance, in the rabbit heart, a single electrical rotor that drifts rapidly throughout the ventricles gives rise to complex patterns of excitation. In the ECG such patterns are indistinguishable from ventricular fibrillation. On the other hand, a rotor that anchors to a discontinuity or defect in the muscle (e.g., a scar, a large artery or a bundle of connective tissue) may result in stationary rotating activity, which in the ECG is manifested as a form of so-called "monomorphic" ventricular tachycardia. More recent data show that ventricular fibrillation occurs in mammals irrespective of size or species. While in small hearts, such as those of mice and rabbits, a single drifting or meandering rotor can result in fibrillation, in larger hearts, such as the sheep and possibly the human, fibrillation occurs in the form of a relatively small number of coexisting but short-lived rotors. Overall, the work discussed here has paved the way for a better understanding of the mechanisms of fibrillation in the normal, as well as diseased human heart. (c) 1998 American Institute of Physics.     

Many-body quantum electrodynamics networks: Non-equilibrium condensed matter physics with light

We review recent developments regarding the quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues, by analogy with atomic physics. We start with quantum impurity models addressing dissipative and driven systems. Both theorists and experimentalists are making efforts towards the characterization of these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect can be characterized by a renormalized light frequency and a peak in the Rayleigh elastic transmission of a photon. We also address the physics of hybrid systems comprising mesoscopic quantum dot devices coupled with an electromagnetic resonator. Then, we discuss extensions to Quantum Electrodynamics (QED) Networks allowing one to engineer the Jaynes–Cummings lattice and Rabi lattice models through the presence of superconducting qubits in the cavities. This opens the door to novel many-body physics with light out of equilibrium, in relation with the Mott–superfluid transition observed with ultra-cold atoms in optical lattices. Then, we summarize recent theoretical predictions for realizing topological phases with light. Synthetic gauge fields and spin–orbit couplings have been successfully implemented in quantum materials and with ultra-cold atoms in optical lattices — using time-dependent Floquet perturbations periodic in time, for example — as well as in photonic lattice systems. Finally, we discuss the Josephson effect related to Bose–Hubbard models in ladder and two-dimensional geometries, producing phase coherence and Meissner currents. The Bose–Hubbard model is related to the Jaynes–Cummings lattice model in the large detuning limit between light and matter (the superconducting qubits). In the presence of synthetic gauge fields, we show that Meissner currents subsist in an insulating Mott phase.     

Dimensional crossover in quantum networks: from macroscopic to mesoscopic physics

We report on magnetoconductance measurements of metallic networks of various sizes ranging from 10 to 10(6) plaquettes, with an anisotropic aspect ratio. Both Altshuler-Aronov-Spivak h/2e periodic oscillations and Aharonov-Bohm h/e periodic oscillations are observed for all networks. For large samples, the amplitude of both oscillations results from the incoherent superposition of contributions of phase coherent regions. When the transverse size becomes smaller than the phase coherent length Lphi, one enters a new regime which is phase coherent (mesoscopic) along one direction and macroscopic along the other, leading to a new size dependence of the quantum oscillations.     

Self-organization of treadmilling filaments

The cytoskeleton is an active network of polar filaments. The activity can lead to the polymerization of filaments at one end and depolymerization at the other. This phenomenon is called treadmilling and is essential for many cellular processes, in particular, the crawling of cells on a substrate. We develop a microscopic theoretical framework for describing systems of treadmilling filaments. We show that such systems can self-organize into structures observed in cell fragments, in particular, asters and moving spots.     

Bose-Einstein condensation and the glassy state

The distinction between a classical glass and a classical liquid is difficult, since both are disordered. The difference is in the fact that a glass is frozen while the liquid is not. In this Letter an equilibrium measure is suggested that distinguishes between a glass and a liquid. The choice of this measure is based on the idea that in a system which is not frozen symmetry under permutation of particles is physically relevant, because particles can be permuted by actual physical motion. This is not the case in a frozen system. In this Letter it is shown how to generalize naturally the quantum mechanical concept of Bose condensed fraction to classical systems in order to distinguish between the glass and the liquid. It is finite in the liquid and zero in the frozen state. The actual value of the condensed fraction in the liquid may serve also as a measure of the glassiness in the liquid.