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https://www.readbyqxmd.com/read/28819262/three-dimensional-imaging-of-vortex-structure-in-a-ferroelectric-nanoparticle-driven-by-an-electric-field
#1
D Karpov, Z Liu, T Dos Santos Rolo, R Harder, P V Balachandran, D Xue, T Lookman, E Fohtung
Topological defects of spontaneous polarization are extensively studied as templates for unique physical phenomena and in the design of reconfigurable electronic devices. Experimental investigations of the complex topologies of polarization have been limited to surface phenomena, which has restricted the probing of the dynamic volumetric domain morphology in operando. Here, we utilize Bragg coherent diffractive imaging of a single BaTiO3 nanoparticle in a composite polymer/ferroelectric capacitor to study the behavior of a three-dimensional vortex formed due to competing interactions involving ferroelectric domains...
August 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28818940/two-dimensional-sp-2-carbon-conjugated-covalent-organic-frameworks
#2
Enquan Jin, Mizue Asada, Qing Xu, Sasanka Dalapati, Matthew A Addicoat, Michael A Brady, Hong Xu, Toshikazu Nakamura, Thomas Heine, Qiuhong Chen, Donglin Jiang
We synthesized a two-dimensional (2D) crystalline covalent organic framework (sp(2)c-COF) that was designed to be fully π-conjugated and constructed from all sp(2) carbons by C=C condensation reactions of tetrakis(4-formylphenyl)pyrene and 1,4-phenylenediacetonitrile. The C=C linkages topologically connect pyrene knots at regular intervals into a 2D lattice with π conjugations extended along both x and y directions and develop an eclipsed layer framework rather than the more conventionally obtained disordered structures...
August 18, 2017: Science
https://www.readbyqxmd.com/read/28812745/hysteresis-and-bonding-reconstruction-in-the-pressure-induced-b3-b1-phase-transition-of-3c-sic
#3
Miguel A Salvadó, R Franco, Pilar Pertierra, T Ouahrani, J M Recio
The determination of kinetic factors affecting phase metastability is crucial for the design of materials out of the ambient conditions. At a given temperature, the kinetic barrier associated with the reconstruction of the bonding network of a pressure-induced phase transition can be only overcome at pressures where the available vibrational energy of the system is equal or higher than the corresponding activation energy. Our work demonstrates that these pressures provide boundaries to hysteresis cycles that can be evaluated following a three-step computational strategy: (i) total energy electronic structure calculations, (ii) determination of vibrational contributions by means of a simple Debye model, and (iii) description of the energetic profile along the transition path in the framework of the martensitic approximation...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28811635/majorana-charges-winding-numbers-and-chern-numbers-in-quantum-ising-models
#4
G Zhang, C Li, Z Song
Mapping a many-body state on a loop in parameter space is a simple way to characterize a quantum state. The connections of such a geometrical representation to the concepts of Chern number and Majorana zero mode are investigated based on a generalized quantum spin system with short and long-range interactions. We show that the topological invariants, the Chern numbers of corresponding Bloch band, is equivalent to the winding number in the auxiliary plane, which can be utilized to characterize the phase diagram...
August 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28811484/sea-of-majorana-fermions-from-pseudo-scalar-superconducting-order-in-three-dimensional-dirac-materials
#5
Morteza Salehi, S A Jafari
We suggest that spin-singlet pseudo-scalar s-wave superconducting pairing creates a two dimensional sea of Majorana fermions on the surface of three dimensional Dirac superconductors (3DDS). This pseudo-scalar superconducting order parameter Δ5, in competition with scalar Dirac mass m, leads to a topological phase transition due to band inversion. We find that a perfect Andreev-Klein reflection is guaranteed by presence of anomalous Andreev reflection along with the conventional one. This effect manifests itself in a resonant peak of the differential conductance...
August 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28811471/two-magnon-scattering-in-the-5d-all-in-all-out-pyrochlore-magnet-cd2os2o7
#6
Thi Minh Hien Nguyen, Luke J Sandilands, C H Sohn, C H Kim, Aleksander L Wysocki, In-Sang Yang, S J Moon, Jae-Hyeon Ko, J Yamaura, Z Hiroi, Tae Won Noh
5d pyrochlore oxides with all-in-all-out magnetic order are prime candidates for realizing strongly correlated, topological phases of matter. Despite significant effort, a full understanding of all-in-all-out magnetism remains elusive as the associated magnetic excitations have proven difficult to access with conventional techniques. Here we report a Raman spectroscopy study of spin dynamics in the all-in-all-out magnetic state of the 5d pyrochlore Cd2Os2O7. Through a comparison between the two-magnon scattering and spin-wave theory, we confirm the large single ion anisotropy in this material and show that the Dzyaloshinskii-Moriya and exchange interactions play a significant role in the spin-wave dispersions...
August 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28811465/lorentz-violating-type-ii-dirac-fermions-in-transition-metal-dichalcogenide-ptte2
#7
Mingzhe Yan, Huaqing Huang, Kenan Zhang, Eryin Wang, Wei Yao, Ke Deng, Guoliang Wan, Hongyun Zhang, Masashi Arita, Haitao Yang, Zhe Sun, Hong Yao, Yang Wu, Shoushan Fan, Wenhui Duan, Shuyun Zhou
Topological semimetals have recently attracted extensive research interests as host materials to condensed matter physics counterparts of Dirac and Weyl fermions originally proposed in high energy physics. Although Lorentz invariance is required in high energy physics, it is not necessarily obeyed in condensed matter physics, and thus Lorentz-violating type-II Weyl/Dirac fermions could be realized in topological semimetals. The recent realization of type-II Weyl fermions raises the question whether their spin-degenerate counterpart-type-II Dirac fermions-can be experimentally realized too...
August 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28809897/topology-optimized-metasurfaces-impact-of-initial-geometric-layout
#8
Jianji Yang, Jonathan A Fan
Topology optimization is a powerful iterative inverse design technique in metasurface engineering and can transform an initial layout into a high-performance device. With this method, devices are optimized within a local design phase space, making the identification of suitable initial geometries essential. In this Letter, we examine the impact of initial geometric layout on the performance of large-angle (75 deg) topology-optimized metagrating deflectors. We find that when conventional metasurface designs based on dielectric nanoposts are used as initial layouts for topology optimization, the final devices have efficiencies around 65%...
August 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28809873/generating-broadband-vortex-modes-in-ring-core-fiber-by-using-a-plasmonic-q-plate
#9
Jingfu Ye, Yan Li, Yanhua Han, Duo Deng, Xiaoya Su, He Song, Jianmin Gao, Shiliang Qu
A mode convertor was proposed and investigated for generating vortex modes in a ring-core fiber based on a plasmonic q-plate (PQP), which is composed of specially organized L-shaped resonator (LSR) arrays. A multicore fiber was used to transmit fundamental modes, and the LSR arrays were used to modulate phases of these fundamental modes. Behind the PQP, the transmitted fundamental modes with gradient phase distribution can be considered as the incident lights for generating broadband vortex modes in the ring-core fiber filter...
August 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28809712/a-novel-intracranial-pressure-readout-circuit-for-passive-wireless-lc-sensor
#10
Fa Wang, Xuan Zhang, Mehdi Shokoueinejad, Bermans J Iskandar, Joshua E Medow, John G Webster
We present a wide frequency range, low cost, wireless intracranial pressure monitoring system, which includes an implantable passive sensor and an external reader. The passive sensor consists of two spiral coils and transduces the pressure change to a resonant frequency shift. The external portable reader reads out the sensor's resonant frequency over a wide frequency range (35 MHz-2.7 GHz). We propose a novel circuit topology, which tracks the system's impedance and phase change at a high frequency with low-cost components...
August 14, 2017: IEEE Transactions on Biomedical Circuits and Systems
https://www.readbyqxmd.com/read/28808984/multiple-gas-phase-conformations-of-a-synthetic-linear-poly-acrylamide-polymer-observed-using-ion-mobility-mass-spectrometry
#11
Jean R N Haler, Johann Far, Abdelhafid Aqil, Jan Claereboudt, Nick Tomczyk, Kevin Giles, Christine Jérôme, Edwin De Pauw
Ion mobility-mass spectrometry (IM-MS) has emerged as a powerful separation and identification tool to characterize synthetic polymer mixtures and topologies (linear, cyclic, star-shaped,…). Electrospray coupled to IM-MS already revealed the coexistence of several charge state-dependent conformations for a single charge state of biomolecules with strong intramolecular interactions, even when limited resolving power IM-MS instruments were used. For synthetic polymers, the sample's polydispersity allows the observation of several chain lengths...
August 14, 2017: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/28805826/violation-of-ohm-s-law-in-a-weyl-metal
#12
Dongwoo Shin, Yongwoo Lee, M Sasaki, Yoon Hee Jeong, Franziska Weickert, Jon B Betts, Heon-Jung Kim, Ki-Seok Kim, Jeehoon Kim
Ohm's law is a fundamental paradigm in the electrical transport of metals. Any transport signatures violating Ohm's law would give an indisputable fingerprint for a novel metallic state. Here, we uncover the breakdown of Ohm's law owing to a topological structure of the chiral anomaly in the Weyl metal phase. We observe nonlinear I-V characteristics in Bi0.96Sb0.04 single crystals in the diffusive limit, which occurs only for a magnetic-field-aligned electric field (E∥B). The Boltzmann transport theory with the charge pumping effect reveals the topological-in-origin nonlinear conductivity, and it leads to a universal scaling function of the longitudinal magnetoconductivity, which completely describes our experimental results...
August 14, 2017: Nature Materials
https://www.readbyqxmd.com/read/28805653/magneto-optical-properties-of-topological-insulator-thin-films-with-broken-inversion-symmetry
#13
Kulsoom Rahim, Ahsan Ullah, Muhammad Tahir, Kashif Sabeeh
We determine the optical response of ultrathin film topological insulators in the presence of a quantizing external magnetic field taking into account both hybridization between surface states, broken inversion symmetry and explicit time reversal symmetry breaking by the magnetic field. We find that breaking of inversion symmetry in the system, which can be due to interaction with a substrate or electrical gating, results in Landau level crossings and opening of additional optical transition channels that were previously forbidden...
August 14, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28805230/the-influence-of-topological-phase-transition-on-the-superfluid-density-of-overdoped-copper-oxides
#14
V R Shaginyan, V A Stephanovich, A Z Msezane, G S Japaridze, K G Popov
We show that a quantum phase transition, generating flat bands and altering Fermi surface topology, is a primary reason for the exotic behavior of the overdoped high-temperature superconductors represented by La2-xSrxCuO4, whose superconductivity features differ from what is predicted by the classical Bardeen-Cooper-Schrieffer theory. This observation can open avenues for chemical preparation of high-Tc materials. We demonstrate that (1) at temperature T = 0, the superfluid density ns turns out to be considerably smaller than the total electron density; (2) the critical temperature Tc is controlled by ns rather than by doping, and is a linear function of the ns; (3) at T > Tc the resistivity ρ(T) varies linearly with temperature, ρ(T) ∝ αT, where α diminishes with Tc → 0, whereas in the normal (non superconducting) region induced by overdoping, Tc = 0, and ρ(T) ∝ T(2)...
August 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28804969/on-chip-andreev-devices-hard-superconducting-gap-and-quantum-transport-in-ballistic-nb-in0-75-ga0-25-as-quantum-well-nb-josephson-junctions
#15
Kaveh Delfanazari, Reuben K Puddy, Pengcheng Ma, Teng Yi, Moda Cao, Yilmaz Gul, Ian Farrer, David A Ritchie, Hannah J Joyce, Michael J Kelly, Charles G Smith
A superconducting hard gap in hybrid superconductor-semiconductor devices has been found to be necessary to access topological superconductivity that hosts Majorana modes (non-Abelian excitation). This requires the formation of homogeneous and barrier-free interfaces between the superconductor and semiconductor. Here, a new platform is reported for topological superconductivity based on hybrid Nb-In0.75 Ga0.25 As-quantum-well-Nb that results in hard superconducting gap detection in symmetric, planar, and ballistic Josephson junctions...
August 14, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28801603/identifying-the-tilt-angle-and-correcting-the-orbital-angular-momentum-spectrum-dispersion-of-misaligned-light-beam
#16
Peng Zhao, Shikang Li, Yu Wang, Xue Feng, Cui Kaiyu, Liu Fang, Wei Zhang, Yidong Huang
The axis tilt of light beam in optical system would introduce the dispersion of orbital angular momentum (OAM) spectrum. To deal with it, a two-step method is proposed and demonstrated. First, the tilt angle of optical axis is identified with a deduced relation between the tilt angle and the variation of OAM topological charges with different reference axes, which is obtained with the help of a charge coupled device (CCD) camera. In our experiments, the precision of measured tilt angle is about 10(-4) rad with topological charges of -3~3...
August 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28798344/2d-surface-optical-lattice-formed-by-plasmon-polaritons-with-application-to-nanometer-scale-molecular-deposition
#17
Yanning Yin, Supeng Xu, Tao Li, Yaling Yin, Yong Xia, Jianping Yin
Surface plasmon polaritons, due to their tight spatial confinement and high local intensity, hold great promises in nanofabrication which is beyond the diffraction limit of conventional lithography. Here, we demonstrate theoretically the 2D surface optical lattices based on the surface plasmon polariton interference field, and the potential application to nanometer-scale molecular deposition. We present the different topologies of lattices generated by simple configurations on the substrate. By explicit theoretical derivations, we explain their formation and characteristics including field distribution, periodicity and phase dependence...
August 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28798297/crystal-structure-of-mppr-1i-a-scp-taps-protein-from-moniliophthora-perniciosa-the-fungus-that-causes-witches-broom-disease-of-cacao
#18
Renata M Baroni, Zhipu Luo, Rabih Darwiche, Elissa M Hudspeth, Roger Schneiter, Gonçalo A G Pereira, Jorge M C Mondego, Oluwatoyin A Asojo
The pathogenic fungi Moniliophthora perniciosa causes Witches' Broom Disease (WBD) of cacao. The structure of MpPR-1i, a protein expressed by M. perniciosa when it infects cacao, are presented. This is the first reported de novo structure determined by single-wavelength anomalous dispersion phasing upon soaking with selenourea. Each monomer has flexible loop regions linking the core alpha-beta-alpha sandwich topology that comprise ~50% of the structure, making it difficult to generate an accurate homology model of the protein...
August 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28796201/enhanced-sensitivity-at-higher-order-exceptional-points
#19
Hossein Hodaei, Absar U Hassan, Steffen Wittek, Hipolito Garcia-Gracia, Ramy El-Ganainy, Demetrios N Christodoulides, Mercedeh Khajavikhan
Non-Hermitian degeneracies, also known as exceptional points, have recently emerged as a new way to engineer the response of open physical systems, that is, those that interact with the environment. They correspond to points in parameter space at which the eigenvalues of the underlying system and the corresponding eigenvectors simultaneously coalesce. In optics, the abrupt nature of the phase transitions that are encountered around exceptional points has been shown to lead to many intriguing phenomena, such as loss-induced transparency, unidirectional invisibility, band merging, topological chirality and laser mode selectivity...
August 9, 2017: Nature
https://www.readbyqxmd.com/read/28794947/quantitative-structure-retention-relationships-for-polycyclic-aromatic-hydrocarbons-and-their-oligoalkynyl-substituted-derivatives
#20
Gaël Rouillé, Cornelia Jäger, Friedrich Huisken, Thomas Henning, Regina Czerwonka, Gabriele Theumer, Carsten Börger, Ingmar Bauer, Hans-Joachim Knölker
Reversed-phase high-performance liquid chromatography (RP-HPLC) has been carried out for a series of unsubstituted polycyclic aromatic hydrocarbons (PAHs) and the corresponding ethynyl, 1,3-butadiynyl, and 1,3,5-hexatriynyl derivatives. Theoretical values of the isotropic polarizability and several polarity descriptors have been computed for each compound by using semiempirical models and density functional theory (DFT), with the aim of evaluating linear functions as quantitative structure-retention relationships (QSRRs)...
August 2017: ChemistryOpen
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