Universal scheme to generate metal-insulator transition in disordered systems

We propose a scheme to generate metal-insulator transition in random binary layer (RBL) model, which is constructed by randomly assigning two types of layers. Based on a tight-binding Hamiltonian, the localization length is calculated for a variety of RBLs with different cross section geometries by using the transfer-matrix method. Both analytical and numerical results show that a band of extended states could appear in the RBLs and the systems behave as metals by properly tuning the model parameters, due to the existence of a completely ordered subband, leading to a metal-insulator transition in parameter space. Furthermore, the extended states are irrespective of the diagonal and off-diagonal disorder strengths. Our results can be generalized to two- and three-dimensional disordered systems with arbitrary layer structures, and may be realized in Bose-Einstein condensates.Comment: 5 ages, 4 figure

Average Density of States in Disordered Graphene systems

In this paper, the average density of states (ADOS) with a binary alloy disorder in disordered graphene systems are calculated based on the recursion method. We observe an obvious resonant peak caused by interactions with surrounding impurities and an anti-resonance dip in ADOS curves near the Dirac point. We also find that the resonance energy (Er) and the dip position are sensitive to the concentration of disorders (x) and their on-site potentials (v). An linear relation, not only holds when the impurity concentration is low but this relation can be further extended to high impurity concentration regime with certain constraints. We also calculate the ADOS with a finite density of vacancies and compare our results with the previous theoretical results.Comment: 10 pages, 8 figure

Experimental investigation of the non-Markovian dynamics of classical and quantum correlations

We experimentally investigate the dynamics of classical and quantum correlations of a Bell diagonal state in a non-Markovian dephasing environment. The sudden transition from classical to quantum decoherence regime is observed during the dynamics of such kind of Bell diagonal state. Due to the refocusing effect of the overall relative phase, the quantum correlation revives from near zero and then decays again in the subsequent evolution. However, the non-Markovian effect is too weak to revive the classical correlation, which remains constant in the same evolution range. With the implementation of an optical $\sigma_{x}$ operation, the sudden transition from quantum to classical revival regime is obtained and correlation echoes are formed. Our method can be used to control the revival time of correlations, which would be important in quantum memory.Comment: extended revision, accepted for publication in Physical Review

Performance of an omnidirectional piezoelectric wind energy harvester

This paper presents a vortex-induced vibration (VIV)-based piezoelectric energy harvester that performs well for all wind directions, a so-called omnidirectional wind energy harvester. The kinetic energy of this harvester stems from wind-induced vibrations of a circular cylinder mounted on an orthogonal bibeam system, rather than a traditional single beam. Wind tunnel testing results show that compared to the traditional single-beam energy harvester, the proposed harvester substantially enhances the effectiveness, in most cases that the beam is skew to the incoming flow. The reasons for the enhancement are explained in detail by examining the wind-induced displacement response components of the cylinder identified by the image processing technique. For all wind directions, both the maximal output energy and the range of effectively working wind speed of the proposed bibeam wind energy harvester are significantly improved with respect to the single-beam system, indicating excellent performance of the proposed omnidirectional harvester in a natural wind environment

A new criteria for zero quantum discord

We propose a new criterion to judge zero quantum discord for arbitrary bipartite states. A bipartite quantum state has zero quantum discord if and only if all blocks of its density matrix are normal matrices and commute with each other. Given a bipartite state with zero quantum discord, how to find out the set of local projectors, which do not disturb the whole state after being imposed on one subsystem, is also presented. A class of two-qubit X-state is used to test the criterion, and an experimental scheme is proposed to realize it. Consequently, we prove that the positive operator-valued measurement can not extinguish the quantum correlation of a bipartite state with nonzero quantum discord.Comment: 10 pages, 1 figur

Imaging defects in vanadium(iii) oxide nanocrystals using Bragg coherent diffractive imaging

Defects in strongly correlated materials such as V2O3 play influential roles on their electrical properties. Understanding the defects' structure is of paramount importance. In this project, we investigate defect structures in V2O3 grown via a flux method. We use AFM to see surface features in several large flake-like particles that exhibit characteristics of spiral growth. We also use Bragg coherent diffractive imaging (BCDI) to probe in 3 dimensions a smaller particle without flake-like morphology and note an absence of the pure screw dislocation characteristic of spiral growth. We identified and measured several defects by comparing the observed local displacement of the crystal, measured via BCDI to well-known models of the displacement around defects in the crystal. We identified two Image ID:d1ce00736j-t1.gif partial dislocations in the crystal. We discuss how defects of different types influence the morphology of V2O3 crystals grown via a flux method

Luminescent hydroxylapatite nanoparticles by surface functionalization

Hydroxylapatite (HA) nanoparticles were functionalized by depositing rare-earth-doped Y2O3Y2O3 nanoparticles on the surface, and the structural evolutions of both HA and Y2O3Y2O3 phases at different annealing temperatures were investigated by x-ray diffraction and transmission electron microscopy. Laser spectroscopy indicated that the surface functionalized HA nanoparticles exhibited strong visible emissions. No visible emissions were observed from rare-earth-doped Y2O3Y2O3 without any substrate, suggesting a doping-induced environmental change of optically active rare-earth elements in the functionalized HA nanoparticles. The luminescent hydroxylapatite nanoparticles may find important applications as a biodegradable substrate for biomarking and drug delivery.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87791/2/183106_1.pd

The algebraic Bethe ansatz for open vertex models

We present a unified algebraic Bethe ansatz for open vertex models which are associated with the non-exceptional $A^{(2)}_{2n},A^{(2)}_{2n-1},B^{(1)}_n,C^{(1)}_n,D^{(1)}_{n}$ Lie algebras. By the method, we solve these models with the trivial K matrix and find that our results agree with that obtained by analytical Bethe ansatz. We also solve the $B^{(1)}_n,C^{(1)}_n,D^{(1)}_{n}$ models with some non-trivial diagonal K-matrices (one free parameter case) by the algebraic Bethe ansatz.Comment: Latex, 35 pages, new content and references are added, minor revisions are mad