arXiv subjects

Yong Sun

Publications and source records attributed to Yong Sun.

54 records · Page 3Linked to original sources

arXiv2017

Magneto-optical conductivity of double Weyl semimetals

We investigate the magneto-optical response of double Weyl semimetals whose energy dispersion is intrinsically anisotropic. We find that in the presence of a magnetic field, the most salient feature of the optical conductivity is a series of resonant peaks with the corresponding frequencies scaling linearly with the strength of the magnetic field. In addition, the optical conductivity is found to be anisotropic, with two of the three longitudinal components residing at a linear background and the remaining one at a constant background. The effects of chemical potential, temperature, impurity scattering, and particle-hole symmetry breaking on the optical conductivity are also studied.

cond-mat.mes-hall↗

arXiv2017

On a problem of Bharanedhar and Ponnusamy involving planar harmonic mappings

In this paper, we give a negative answer to a problem presented by Bharanedhar and Ponnusamy (Rocky Mountain J. Math. 44: 753--777, 2014) concerning univalency of a class of harmonic mappings. More precisely, we show that for all values of the involved parameter, this class contains a non-univalent function. Moreover, several results on a new subclass of close-to-convex harmonic mappings, which is motivated by work of Ponnusamy and Sairam Kaliraj (Mediterr. J. Math. 12: 647--665, 2015), are obtained.

math.CV↗

arXiv2017

Unidirectional zero reflection as gauged parity-time symmetry

We introduce here the concept of establishing Parity-time symmetry through a gauge transformation involving a shift of the mirror plane for the Parity operation. The corresponding unitary transformation on the system's constitutive matrix allows us to generate and explore a family of equivalent Parity-time symmetric systems. We further derive that unidirectional zero reflection can always be associated with a gauged PT-symmetry and demonstrate this experimentally using a microstrip transmission-line with magnetoelectric coupling. This study allows us to use bianisotropy as a simple route to realize and explore exceptional point behaviour of PT-symmetric or generally non-Hermitian systems.

physics.class-ph↗

arXiv2017

RKKY interaction of magnetic impurities in multi-Weyl semimetals

We have systematically investigated the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two magnetic impurities in Weyl semimetals with arbitrary monopole charge $Q$. We find that the RKKY interaction becomes intrinsically anisotropic for $Q\geq2$, and its dependence on Fermi energy and impurity separation is directly controlled by the monopole charge. With the increase of $Q$, the RKKY interaction becomes more long-ranged and more anisotropic, which makes interesting magnetic orders easier to form and thus may have important applications in spintronics.

cond-mat.mes-hall↗

arXiv2017

SFCSD: A Self-Feedback Correction System for DNS Based on Active and Passive Measurement

Domain Name System (DNS), one of the important infrastructure in the Internet, was vulnerable to attacks, for the DNS designer didn't take security issues into consideration at the beginning. The defects of DNS may lead to users' failure of access to the websites, what's worse, users might suffer a huge economic loss. In order to correct the DNS wrong resource records, we propose a Self-Feedback Correction System for DNS (SFCSD), which can find and track a large number of common websites' domain name and IP address correct correspondences to provide users with a real-time auto-updated correct (IP, Domain) binary tuple list. By matching specific strings with SSL, DNS and HTTP traffic passively, filtering with the CDN CNAME and non-homepage URL feature strings, verifying with webpage fingerprint algorithm, SFCSD obtains a large number of highly possibly correct IP addresses to make an active manual correction in the end. Its self-feedback mechanism can expand search range and improve performance. Experiments show that, SFCSD can achieve 94.3% precision and 93.07% recall rate with the optimal threshold selection in the test dataset. It has 8Gbps processing speed stand-alone to find almost 1000 possibly correct (IP, Domain) per day for the each specific string and to correct almost 200.

cs.NI↗

arXiv2017

On third Hankel determinants for subclasses of analytic functions and close-to-convex harmonic mappings

In this paper, we obtain the upper bounds to the third Hankel determinants for starlike functions of order $α$, convex functions of order $α$ and bounded turning functions of order $α$. Furthermore, several relevant results on a new subclass of close-to-convex harmonic mappings are obtained. Connections of the results presented here to those that can be found in the literature are also discussed.

math.CV↗

arXiv2015

Simulation of Zitterbewegung by modelling the Dirac equation in Metamaterials

We develop a dynamic description of an effective Dirac theory in metamaterials, in which the wavefunction is modeled by the corresponding electric and magnetic field in the metamaterial. This electro-magnetic field can be probed in the experimental setup, which means that the wavefunction of the effective theory is directly accessible by measurement. Our model is based on a plane wave expansion, which ravels the identification of Dirac spinors with single-frequency excitations of the electro-magnetic field in the metamaterial. The characteristic Zitterbewegung is shown to emerge in simulations of the effective theory and we verify this signature with an analytic solution.

quant-ph↗

arXiv2012

Photonic simulation of topological excitations in metamaterials

Condensed matter systems with topological order and metamaterials with left-handed chirality have attracted recently extensive interests in the fields of physics and optics. So far the two fields are independent, and there is no work to address their connection. Here we propose to establish the relation between the topological order in condensed matter systems and the chirality in metamaterials, by mapping explicitly Maxwell's equations to the Dirac equation in one dimension. We report an experimental implement of the band inversion in the Dirac equation, which accompanies change of chirality of electromagnetic wave in metamaterials, and the first microwave measurement of topological excitations and topological phases in one dimension. Our finding provides a proof-of-principle example that electromagnetic wave in the metamaterials can be used to simulate the topological order in condensed matter systems and quantum phenomena in relativistic quantum mechanics in a controlled laboratory environment.

physics.optics↗

arXiv2006

Investigating Diffusion Coefficient Using Dynamic Light Scattering Technique

In this work, the Z-average, effective, apparent diffusion coefficients and their poly-dispersity indexes were investigated for dilute poly-disperse homogeneous spherical particles in dispersion where the Rayleigh-Gans-Debye approximation is valid. The results reveal that the values of the apparent and effective diffusion coefficients at a scattering angle investigated are consistent and the difference between the effective and Z-average diffusion coefficients is a function of the mean particle size, size distribution and scattering angle. For the small particles with narrow size distributions, the Z-average diffusion coefficient can be got directly at any scattering angle. For the small particles with wide size distributions, the Z-average diffusion coefficient should be measured at a small scattering angle. For large particles, in order to obtain a good approximate value of Z-average diffusion coefficient, the wider the particle size distribution, the smaller the scattering angle that the DLS data are measured. The poly-dispersity index of the effective diffusion coefficient at a scattering angle investigated is consistent with that of the Z-average diffusion coefficient and without considering the influences of noises, the difference between the poly-dispersity indexes of the Z-average and apparent diffusion coefficients is determined by the mean particle size, size distribution and scattering angle together.

physics.chem-ph↗

arXiv2006

Investigating Auto-correlation of Scattered Light of Mixed Particles

In this work, the normalized time auto-correlation function of the electric field of the light $g^{(1)}(τ)$ that is scattered by the two kinds of particles in dispersion is investigated. The results show that the logarithm of $g^{(1)}(τ)$ can be consistent with a line and many reasons can cause the deviations between an exponentiality and plots of $g^{(1)}(τ)$ as a function of delay time $τ$. The nonexponentiality of $g^{(1)}(τ)$ is not only determined by the particle size distribution and scattering angle but also greatly influenced by the relationship between the concentrations, mass densities and the values that the refractive index of the material expands as a function of the concentration of the two kinds of particles.

physics.chem-ph↗

arXiv2005

Auto-correlation Function Analysis of Scattered Light Intensity at Different Scattering Angles

In this work, the effects of the scattering angle on the nonexponentiality of the normalized time auto-correlation function of the scattered light intensity $g^{(2)}(τ) $ are investigated using dilute Poly($N$-isopropylacrylamide) microgel and standard polystyrene latex samples in dispersion respectively. The results show that the influences of the scattering angle on the deviation between an exponentiality and $% g^{(2)}(τ) $ are small. With the assistance of the simulated data of $g^{(2)}(τ) $, the effects of the particle size distribution and scattering angle on the deviation between an exponentiality and $g^{(2)}(τ) $ are explored. The analysis reveals that the nonexponentiality of $% g^{(2)}(τ) $ is determined by the particle size distribution and scattering angle. In general, the influences of the particle size distribution are small on the nonexponentiality of $g^{(2)}(τ) $ and very large on the initial slope of the logarithm of $g^{(2)}(τ) $ and the effects of the scattering angle are determined by the particle size distribution and mean particle size. Under some conditions, the deviation between an exponentiality and $g^{(2)}(τ) $ is greatly influenced by the scattering angle. The values of the apparent hydrodynamic radius are also determined by the particle size distribution and scattering angle. The apparent hydrodynamic radius and its distribution obtained using the cumulants method are different from the hydrodynamic radius and its distribution.

physics.chem-ph↗

arXiv2005

New Interpretation for Laser Light Scattering Technique

The new method proposed in this work not only measures the particle size distribution and the average molar mass accurately using the static light scattering (SLS) technique when the Rayleigh-Gans-Debye approximation is valid for dilute poly-disperse homogenous spherical particles in dispersion, but also enables us to have insight into the theoretical analysis of the dimensionless shape parameter $ρ$. With the method, a new size, static radii $R_{s}$, can be measured. Based on the new static particle size information, detailed investigation of the normalized time auto-correlation function of the scattered light intensity $g^{(2)}(τ)$ reveals that there exist three different particle sizes: the static radius, hydrodynamic radius and apparent hydrodynamic radius that is the hydrodynamic radius obtained using the cumulants method. With a simple assumption that the hydrodynamic radius $R_{h}$ is in proportion to the static radius $R_{s}$, the expected values of $g^{(2)}(τ) $ calculated based on the static and commercial particle size information are consistent with the experimental data. With the assistance of simulated data, the apparent hydrodynamic radius is discussed. The results show that the apparent hydrodynamic radius is different from the mean hydrodynamic radius and is determined by the optical, hydrodynamic characteristics and size distribution of particles and scattering vector. The analysis also reveals that $ρ$ is determined by not only the structure of particles but also the relationship between the optical and hydrodynamic characteristics of particles even for mono-disperse model.

physics.chem-ph↗

arXiv2005

Investigation of Volume Phase Transition from the Different Properties of Particles

In this work, three different particle sizes: the static radius $R_{s}$, hydrodynamic radius $R_{h}$ and apparent hydrodynamic radius $ R_{h,app}$ obtained using the light scattering technique, are investigated for dilute poly-disperse homogenous spherical particles with a simple assumption that the hydrodynamic radius is in proportion to the static radius, when the Rayleigh-Gans-Debye approximation is valid. The results show that the expected values of the normalized time auto-correlation function of the scattered light intensity $g^{(2)}(τ) $ calculated based on the static particle size information are consistent with the experimental data. The volume phase transition is thus investigated using the equilibrium swelling ratios of static radii and apparent hydrodynamic radii respectively. The changes of the static particle size information and apparent hydrodynamic radius as a function of temperature $T$ show the effects of the volume phase transition on optical properties and the total influences of the volume phase transition on the optical, hydrodynamic characteristics and size distribution of particles, respectively. The effects of cross-linker on the volume phase transition are also discussed.

physics.chem-ph↗

arXiv2005

Auto-correlation Function Study of Scattered Light Intensity

In this work, the particle size distribution measured using the dynamic light scattering (DLS) technique is compared with that obtained from the static light scattering (SLS) technique or provided by the supplier measured using the Transmission Electron Microscopy (TEM) technique for dilute Poly($N$-isopropylacrylamide) microgel and standard polystyrene latex samples in dispersion respectively. The results show that the narrow particle size distribution that can be measured accurately using the SLS technique is not suited to the determination by the DLS technique and the particle size distribution obtained from the DLS technique is different from the value provided by the supplier. With the assistance of the simulated data of the normalized time auto-correlation function of the scattered light intensity $g^{(2)}(τ)$, the effects of the particle size distribution on the nonexponentiality of $g^{(2)}(τ)$ measured at a scattering angle of 30$^\mathrm o$ are investigated. The analysis reveals that the influences of the particle size distribution are small on the nonexponentiality of $g^{(2)}(τ)$ and very large on the initial slope of the logarithm of $g^{(2)}(τ)$. The values of the apparent hydrodynamic radius are also largely influenced by the particle size distribution and the difference between the distributions of the apparent hydrodynamic radius and hydrodynamic radius of particles is determined by the method of cumulants.

physics.chem-ph↗

arXiv2004

Different Particle Sizes Obtained from Static and Dynamic Laser Light Scattering

Detailed investigation of static and dynamic laser light scattering has been attempted in this work both theoretically and experimentally based on dilute water dispersions of two different homogenous spherical particles, polystyrene latexes and poly($N$-isopropylacrylamide) microgels. When Rayleigh-Gans-Debye approximation is valid, a new radius $R_{s}$, referred to as a static radius, can be obtained from the static light scattering $(SLS) $. If the absolute magnitude of the scattered intensity and some constants that are related to the instrument and samples are known, the average molar mass for large particles can be measured. The size information obtained from SLS is purely related to the optical properties of particles, i.e., to $R_{s}$ and its distribution $G(R_{s}) $. The size information obtained from dynamic light scattering $(DLS) $ is more complicated, the size distribution of which is a composite distribution that is not only related to the optical properties of particles, but also related to the hydrodynamic properties and the scattering vector. Strictly speaking, an apparent hydrodynamic radius $R_{h,app}$ is a composite size obtained from averaging the term $\exp (-q^{2}Dτ) $ in the static size distribution $G(R_{s}) $, with the weight $R_{s}^{6}P(q,R_{s}) $ that is also a function of both $R_{s}$ and the scattering vector $q$.

physics.bio-ph↗

arXiv2004

Size Information Obtained by Using Static Light Scattering Technique

Detailed investigation of static light scattering $(SLS) $ has been attempted in this work using dilute water dispersions of homogenous spherical particles, poly($N$-isopropylacrylamide) microgels and simulated data. When Rayleigh-Gan-Debye approximation is valid, for large particles, the simple size information, the static radius $R_{s}$ and distribution $G(R_{s}) $, can be accurately obtained from SLS. For small particles, the root mean-square radius of gyration $< R_{g}^{2}>_{Zimm}^{1/2}$ and the molar mass of particles measured using the Zimm plot are discussed. The results show that the molar mass measured using the Zimm plot over the average molar mass of particles is a function of the size distribution. With the assistance of simulated data, the effects of the reflected light and noises have been investigated in detail. Measuring the static radius from the SLS data provides one method to avoid the stringent requirements for the sample quantity and the instrument capability at small scattering angles.

physics.chem-ph↗

arXiv2004

Discussing the Relationship between the Static and Dynamic Light Scattering

Both the static $(SLS) $ and dynamic $(DLS) $ light scattering techniques are used to obtain the size information from the scattered intensity, but the static radius $R_{s}$ and the apparent hydrodynamic radius $R_{h,app}$ are different. In this paper, the relationship between SLS and DLS is discussed using dilute water dispersions of two different homogenous spherical particles, polystyrene latexes and poly($N$-isopropylacrylamide) microgels, with a simple assumption that the hydrodynamic radius $R_{h}$ is in proportion to the static radius $R_{s}$, when Rayleigh-Gans-Debye approximation is valid. With the assistance of the simulated data, the apparent hydrodynamic radius $R_{h,app}$ has been discussed. The results show that the apparent hydrodynamic radius is different with the mean hydrodynamic radius of particles and is a composite size obtained from averaging the term $\exp (-q^{2}Dτ) $ in the static size distribution $G(R_{s}) $ with the weight $R_{s}^{6}P(q,R_{s}) $.

physics.chem-ph↗

arXiv2004

Three Different Sizes Obtained Using Light Scattering Techniques

The average scattered intensity is determined by the optical characteristics of particles in dispersion. The normalized time auto-correlation function of the scattered light intensity $g^{(2)}(τ) $ includes both the optical and hydrodynamic information of particles. From the different characteristics of particles, the particle sizes can be obtained. In this paper, three sizes: the static radius $R_{s}$, the hydrodynamic radius $R_{h}$ and the apparent hydrodynamic radius $R_{h,app}$ are discussed using dilute water dispersions of homogenous spherical particles poly($N$-isopropylacrylamide) microgels, with a simple assumption that the hydrodynamic radius is in proportion to the static radius, when Rayleigh-Gans-Debye approximation is valid. Our results show that the expected values of the normalized time auto-correlation function of the scattered light intensity are consistent with the experimental data very well and the difference between the static radius and the apparent hydrodynamic radius is large and the difference between the hydrodynamic radius and the apparent hydrodynamic radius is influenced by the particle size distribution.

physics.chem-ph↗