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Chuang Li, Lun-Hui Hu, Yi Zhou, Fu-Chun Zhang
Sau, Lutchyn, Tewari and Das Sarma (SLTD) proposed a heterostructure consisting of a semiconducting thin film sandwiched between an s-wave superconductor and a magnetic insulator and showed possible Majorana zero mode. Here we study spin polarization of the vortex core states and spin selective Andreev reflection at the vortex center of the SLTD model. In the topological phase, the differential conductance at the vortex center contributed from the Andreev reflection, is spin selective and has a quantized value [Formula: see text] at zero bias...
May 18, 2018: Scientific Reports
Andreas Brechtel, Philipp Gramlich, Daniel Ritterskamp, Barbara Drossel, Thilo Gross
We study diffusion-driven pattern formation in networks of networks, a class of multilayer systems, where different layers have the same topology, but different internal dynamics. Agents are assumed to disperse within a layer by undergoing random walks, while they can be created or destroyed by reactions between or within a layer. We show that the stability of homogeneous steady states can be analyzed with a master stability function approach that reveals a deep analogy between pattern formation in networks and pattern formation in continuous space...
March 2018: Physical Review. E
M Garzon, L J Gray, J A Sethian
The coalescence, and subsequent satellite formation, of two inviscid droplets is studied numerically. The initial drops are taken to be of equal and different sizes, and simulations have been carried out with and without the presence of an electrical field. The main computational challenge is the tracking of a free surface that changes topology. Coupling level set and boundary integral methods with an embedded potential flow model, we seamlessly compute through these singular events. As a consequence, the various coalescence modes that appear depending upon the relative ratio of the parent droplets can be studied...
March 2018: Physical Review. E
Yu-Zhong Chen, Ying-Cheng Lai
Revealing the structure and dynamics of complex networked systems from observed data is a problem of current interest. Is it possible to develop a completely data-driven framework to decipher the network structure and different types of dynamical processes on complex networks? We develop a model named sparse dynamical Boltzmann machine (SDBM) as a structural estimator for complex networks that host binary dynamical processes. The SDBM attains its topology according to that of the original system and is capable of simulating the original binary dynamical process...
March 2018: Physical Review. E
K Haydukivska, V Blavatska
We consider the complex polymer system, consisting of a ring polymer connected to the f_{1}-branched starlike structure, in a good solvent in the presence of structural inhomogeneities. In particular cases f_{1}=1 and f_{1}=2, such a system restores the synthesized tadpole-shaped polystyrenes [Doi et al., Macromolecules 46, 1075 (2013)MAMOBX0024-929710.1021/ma302511j]. We assume that structural defects are correlated at large distances x according to a power law x^{-a}. Applying the direct polymer renormalization approach, we evaluate the universal size characteristics such as the ratio of the radii of gyration of star-ring and star topologies, and compare the effective sizes of single arms in complex structures and isolated polymers of the same total molecular weight...
March 2018: Physical Review. E
Raj Kumar Pal, Javier Vila, Michael Leamy, Massimo Ruzzene
This work investigates the effect of nonlinearities on topologically protected edge states in one- and two-dimensional phononic lattices. We first show that localized modes arise at the interface between two spring-mass chains that are inverted copies of each other. Explicit expressions derived for the frequencies of the localized modes guide the study of the effect of cubic nonlinearities on the resonant characteristics of the interface, which are shown to be described by a Duffing-like equation. Nonlinearities produce amplitude-dependent frequency shifts, which in the case of a softening nonlinearity cause the localized mode to migrate to the bulk spectrum...
March 2018: Physical Review. E
Gard Spreemann, Benjamin Dunn, Magnus Bakke Botnan, Nils A Baas
We propose a method, based on persistent homology, to uncover topological properties of a priori unknown covariates in a system governed by the kinetic Ising model with time-varying external fields. As its starting point the method takes observations of the system under study, a list of suspected or known covariates, and observations of those covariates. We infer away the contributions of the suspected or known covariates, after which persistent homology reveals topological information about unknown remaining covariates...
March 2018: Physical Review. E
Muhammed Rasi M, K P Zuhail, Arun Roy, Surajit Dhara
The competing effect of surface anchoring of dispersed microparticles and elasticity of nematic and cholesteric liquid crystals has been shown to stabilize a variety of topological defects. Here we study a pair of colloidal microparticles with homeotropic and planar surface anchoring across N-SmA-SmC phase transitions. We show that below the SmA-SmC phase transition the temperature dependence of interparticle separation (D) of colloids with homeotropic anchoring shows a power-law behavior; D∼(1-T/T_{AC})^{α}, with an exponent α≈0...
March 2018: Physical Review. E
Fabio C Zegarra, Dirar Homouz, Yossi Eliaz, Andrei G Gasic, Margaret S Cheung
We investigated the impact of hydrodynamic interactions (HI) on protein folding using a coarse-grained model. The extent of the impact of hydrodynamic interactions, whether it accelerates, retards, or has no effect on protein folding, has been controversial. Together with a theoretical framework of the energy landscape theory (ELT) for protein folding that describes the dynamics of the collective motion with a single reaction coordinate across a folding barrier, we compared the kinetic effects of HI on the folding rates of two protein models that use a chain of single beads with distinctive topologies: a 64-residue α/β chymotrypsin inhibitor 2 (CI2) protein, and a 57-residue β-barrel α-spectrin Src-homology 3 domain (SH3) protein...
March 2018: Physical Review. E
Diamantino C da Silva, Ginestra Bianconi, Rui A da Costa, Sergey N Dorogovtsev, José F F Mendes
We study complex networks formed by triangulations and higher-dimensional simplicial complexes representing closed evolving manifolds. In particular, for triangulations, the set of possible transformations of these networks is restricted by the condition that at each step, all the faces must be triangles. Stochastic application of these operations leads to random networks with different architectures. We perform extensive numerical simulations and explore the geometries of growing and equilibrium complex networks generated by these transformations and their local structural properties...
March 2018: Physical Review. E
Rajiv Kumar Jha, Priyanka Tare, Valakunja Nagaraja
DNA gyrase introduces negative supercoils into DNA to maintain topological homeostasis. The genes encoding gyrase, gyrB and gyrA, form a dicistronic operon in Mycobacterium tuberculosis (Mtb) and other actinobacteria. Earlier work indicated that DNA relaxation stimulates the expression of the gyr genes, a phenomenon termed relaxation-stimulated transcription (RST). The present study addresses the underlying mechanism of gyr operon regulation. The operon is regulated by overlapping and divergently oriented promoters located upstream of gyrB...
May 15, 2018: Biochemical and Biophysical Research Communications
Maxim Trushin, Mark Oliver Goerbig, Wolfgang Belzig
Using the quasiclassical concept of Berry curvature we demonstrate that a Dirac exciton-a pair of Dirac quasiparticles bound by Coulomb interactions-inevitably possesses an intrinsic angular momentum making the exciton effectively self-rotating. The model is applied to excitons in two-dimensional transition metal dichalcogenides, in which the charge carriers are known to be described by a Dirac-like Hamiltonian. We show that the topological self-rotation strongly modifies the exciton spectrum and, as a consequence, resolves the puzzle of the overestimated two-dimensional polarizability employed to fit earlier spectroscopic measurements...
May 4, 2018: Physical Review Letters
A Deblais, T Barois, T Guerin, P H Delville, R Vaudaine, J S Lintuvuori, J F Boudet, J C Baret, H Kellay
Simple ingredients, such as well-defined interactions and couplings for the velocity and orientation of self-propelled objects, are sufficient to produce complex collective behavior in assemblies of such entities. Here, we use assemblies of rodlike robots made motile through self-vibration. When confined in circular arenas, dilute assemblies of these rods act as a gas. Increasing the surface fraction leads to a collective behavior near the boundaries: polar clusters emerge while, in the bulk, gaslike behavior is retained...
May 4, 2018: Physical Review Letters
Yiwen Zhang, Ang Chen, Wenzhe Liu, Chia Wei Hsu, Bo Wang, Fang Guan, Xiaohan Liu, Lei Shi, Ling Lu, Jian Zi
The vortex, a fundamental topological excitation featuring the in-plane winding of a vector field, is important in various areas such as fluid dynamics, liquid crystals, and superconductors. Although commonly existing in nature, vortices were observed exclusively in real space. Here, we experimentally observed momentum-space vortices as the winding of far-field polarization vectors in the first Brillouin zone of periodic plasmonic structures. Using homemade polarization-resolved momentum-space imaging spectroscopy, we mapped out the dispersion, lifetime, and polarization of all radiative states at the visible wavelengths...
May 4, 2018: Physical Review Letters
Fei Xue, A H MacDonald
We study the phase diagram of a model quantum spin Hall system as a function of band inversion and band-coupling strength, demonstrating that when band hybridization is weak, an interaction-induced nematic insulator state emerges over a wide range of band inversion. This property is a consequence of the long-range Coulomb interaction, which favors interband phase coherence that is weakly dependent on momentum and therefore frustrated by the single-particle Hamiltonian at the band inversion point. For weak band hybridization, interactions convert the continuous gap closing topological phase transition at inversion into a pair of continuous phase transitions bounding a state with broken time-reversal and rotational symmetries...
May 4, 2018: Physical Review Letters
Sabrina Palazzese, Javier F Landaeta, Diego Subero, Ernst Bauer, Ismardo Bonalde
In this work we aim to analyze the effect of a strong antisymmetric spin-orbit coupling (ASOC) on superconductivity of noncentrosymmetric LaPtSi. We study the energy gap structure of polycrystalline LaPtSi by using magnetic penetration depth measurements down to 0.02$T_c$. We observed a dirty s-wave behavior, which firmly evidence that the spin-singlet component of the mixed pairing state is highly dominant. This is consistent with previous results in the sense that the mere presence of a strong ASOC does not lead to unconventional behaviors...
May 18, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Shanna Zhu, Dechao Meng, Genhao Liang, Gang Shi, Peng Zhao, Peng Cheng, Yongqing Li, Xiaofang Zhai, Yalin Lu, Lan Chen, Kehui Wu
Inducing magnetism in a topological insulator (TI) by exchange coupling with a ferromagnetic insulator (FMI) will break the time-reversal symmetry of topological surface states, offering possibilities to realize several predicted novel magneto-electric effects. Seeking suitable FMI materials is crucial for the coupling of heterojunctions, and yet is challenging as well and only a few kinds have been explored. In this report, we introduce epitaxial LaCoO3 thin films on a SrTiO3 substrate, which is an insulating ferromagnet with a Curie temperature of TC ∼ 85 K, to be combined with TIs for proximity coupling...
May 18, 2018: Nanoscale
Xiang Zhao, Edward T Nguyen, Anh N Hong, Pingyun Feng, Xianhui Bu
Homochiral metal-organic frameworks (MOFs) are an important class of chiral solids with potential applications in chiral recognition; however, relatively few are available. Of great importance is the availability of low-cost, racemization-resistant, and versatile enantiopure building blocks. Among chiral building blocks, d-camphoric acid is highly prolific, yet, its trans-isomer, l-isocamphoric acid, has remained unknown in the entire field of solid-state materials. Its rich yet totally untapped synthetic and structural chemistry has now been investigated through the synthesis of a large family of homochiral metal isocamphorates...
May 17, 2018: Angewandte Chemie
Jin-Zhong Gu, Yan Cai, Zi-Yue Qian, Min Wen, Zi-Fa Shi, Dong-Yu Lv, Alexander M Kirillov
This study reports the hydrothermal synthesis of a novel series of twelve coordination compounds, namely, {[Cd(μ-Hnbtc)(H2O)4]·H2O}n (1), [Zn2(μ-Hnbtc)2(phen)2]·2H2O (2), [Zn(Hnbtc)(phen)2(H2O)]·4.5H2O (3), [Ni(Hnbtc)(phen)2(H2O)]·6H2O (4), [Zn2(μ-Hnbtc)2(2,2'-bipy)2]·2H2O (5), [Cd3(μ5-nbtc)(μ6-nbtc)(2,2'-bipy)2(H2O)]n (6), {[Zn3(μ3-nbtc)2(phen)3(H2O)2]·4H2O} (7), [Co(H2O)6][Co2(nbtc)2(μ-4,4'-bipy)(4,4'-bipy)2(H2O)6]·8H2O (8), {[Ni3(μ4-nbtc)2(μ-4,4'-bipy)2.5(μ-H2O)(H2O)3]·4H2O}n (9), {[Cd2(μ4-nbtc)(μ-OH)(2,2'-bipy)2]·H2O}n (10), [Cd2(μ4-nbtc)(μ-OH)(phen)2(H2O)]n (11), and {[Zn2(μ5-nbtc)(μ3-OH)(μ-4,4'-bipy)]·4,4'-bipy·H2O}n (12), which are derived from 3'-nitro-biphenyl-2,4,4'-tricarboxylic acid (H3nbtc) as a virtually unexplored building block...
May 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
John A Lees, Michelle Kendall, Julian Parkhill, Caroline Colijn, Stephen D Bentley, Simon R Harris
Background : Phylogenetic reconstruction is a necessary first step in many analyses which use whole genome sequence data from bacterial populations. There are many available methods to infer phylogenies, and these have various advantages and disadvantages, but few unbiased comparisons of the range of approaches have been made. Methods : We simulated data from a defined "true tree" using a realistic evolutionary model. We built phylogenies from this data using a range of methods, and compared reconstructed trees to the true tree using two measures, noting the computational time needed for different phylogenetic reconstructions...
2018: Wellcome Open Research
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