Consensus analysis of multi-agent systems under switching topologies by a topology-dependent average dwell time approach

© The Institution of Engineering and Technology 2016. This study addresses the consensus problem for a class of any order multi-agent systems under switching topologies which could include kinds of unconsensusable topologies. The consensus problem, depending on structure properties and the corresponding topology, is researched with fixed structure properties under directed switching topologies. By the properties of Laplacian matrix, the consensus problem for multi-agent systems is converted into the stability problem of the corresponding switched systems with a Laplacian-like matrix. Some sufficient conditions for consensus are presented by using the dwell time approach. Finally, numerical examples and the results of computer simulation are given to verify the theoretical analysis

Fractional Quantum Hall Effect of Hard-Core Bosons in Topological Flat Bands

Recent proposals of topological flat band (TFB) models have provided a new route to realize the fractional quantum Hall effect (FQHE) without Landau levels. We study hard-core bosons with short-range interactions in two representative TFB models, one of which is the well known Haldane model (but with different parameters). We demonstrate that FQHE states emerge with signatures of even number of quasi-degenerate ground states on a torus and a robust spectrum gap separating these states from higher energy spectrum. We also establish quantum phase diagrams for the filling factor 1/2 and illustrate quantum phase transitions to other competing symmetry-breaking phases.Comment: 4 pages, 6 figure

Implementing topological quantum manipulation with superconducting circuits

A two-component fermion model with conventional two-body interactions was recently shown to have anyonic excitations. We here propose a scheme to physically implement this model by transforming each chain of two two-component fermions to the two capacitively coupled chains of superconducting devices. In particular, we elaborate how to achieve the wanted operations to create and manipulate the topological quantum states, providing an experimentally feasible scenario to access the topological memory and to build the anyonic interferometry.Comment: 4 pages with 3 figures; V2: published version with minor updation

Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion Compound CeIrIn_5:NQR Evidence

We report measurements of the ^{115}In nuclear spin-lattice relaxation rate (1/T_1) between T=0.09 K and 100 K in the new heavy fermion (HF) compound CeIrIn_5. At 0.4 K < T < 100 K, 1/T_1 is strongly T-dependent, which indicates that CeIrIn_5 is much more itinerant than known Ce-based HFs. We find that 1/T_1T, subtracting that for LaIrIn_5, follows a 1/(T+\theta)^{3/4} variation with \theta=8 K. We argue that this novel feature points to anisotropic, due to a layered crystal structure, spin fluctuations near a magnetic ordering. The bulk superconductivity sets in at 0.40 K below which the coherence peak is absent and 1/T_1 follows a T^3 variation, which suggests unconventional superconductivity with line-node gap.Comment: minor changes, appeared in PRL (4 pages, 4 figures

Na content dependence of superconductivity and the spin correlations in Na_{x}CoO_{2}\cdot 1.3H_{2}O

We report systematic measurements using the ^{59}Co nuclear quadrupole resonance(NQR) technique on the cobalt oxide superconductors Na_{x}CoO_{2}\cdot 1.3H_{2}O over a wide Na content range x=0.25\sim 0.34. We find that T_c increases with decreasing x but reaches to a plateau for x \leq0.28. In the sample with x \sim 0.26, the spin-lattice relaxation rate 1/T_1 shows a T^3 variation below T_c and down to T\sim T_c/6, which unambiguously indicates the presence of line nodes in the superconducting (SC) gap function. However, for larger or smaller x, 1/T_1 deviates from the T^3 variation below T\sim 2 K even though the T_c (\sim 4.7 K) is similar, which suggests an unusual evolution of the SC state. In the normal state, the spin correlations at a finite wave vector become stronger upon decreasing x, and the density of states at the Fermi level increases with decreasing x, which can be understood in terms of a single-orbital picture suggested on the basis of LDA calculation.Comment: version published in J. Phys. Condens. Matter (references updated and more added