arXiv subjects

Jian Wang

Publications and source records attributed to Jian Wang.

At least 1,171 records · Page 65Linked to original sources

arXiv2013

How to improve the prediction based on citation impact percentiles for years shortly after the publication date?

The findings of Bornmann, Leydesdorff, and Wang (in press) revealed that the consideration of journal impact improves the prediction of long-term citation impact. This paper further explores the possibility of improving citation impact measurements on the base of a short citation window by the consideration of journal impact and other variables, such as the number of authors, the number of cited references, and the number of pages. The dataset contains 475,391 journal papers published in 1980 and indexed in Web of Science (WoS, Thomson Reuters), and all annual citation counts (from 1980 to 2010) for these papers. As an indicator of citation impact, we used percentiles of citations calculated using the approach of Hazen (1914). Our results show that citation impact measurement can really be improved: If factors generally influencing citation impact are considered in the statistical analysis, the explained variance in the long-term citation impact can be much increased. However, this increase is only visible when using the years shortly after publication but not when using later years.

cs.DL↗

arXiv2013

Continuously tunable electronic structure of transition metal dichalcogenides superlattices

Two dimensional transition metal dichalcogenides (TMDC) have very interesting properties for optoelectronic devices. In this work we theoretically investigate and predict that superlattices comprised of MoS$_{2}$ and WSe$_{2}$ multilayers possess continuously tunable electronic structure having direct band gap. The tunability is controlled by the thickness ratio of MoS$_{2}$ versus WSe$_{2}$ of the superlattice. When this ratio goes from 1:2 to 5:1, the dominant K-K direct band gap is continuously tuned from 0.14 eV to 0.5 eV. The gap stays direct against -0.6% to 2% in-layer strain and up to -4.3% normal-layer compressive strain. The valance and conduction bands are spatially separated. These robust properties suggest that MoS$_{2}$ and WSe$_{2}$ multilayer superlattice should be an exciting emerging material for infrared optoelectronics.

cond-mat.mtrl-sci↗

arXiv2013

Electronic transport properties of topological insulator films and low dimensional superconductors

In this review, we present a summary of some recent experiments on topological insulators (TIs) and superconducting nanowires and films. Electron-electron interaction (EEI), weak anti-localization (WAL) and anisotropic magneto-resistance (AMR) effect found in TI films by transport measurements are reported. Then, transport properties of superconducting films, bridges and nanowires and proximity effect in non-superconducting nanowires are described. Finally, the interplay between TIs and superconductors (SCs) is also discussed.

cond-mat.mes-hall↗

arXiv2013

Demonstration of surface transport in a hybrid Bi2Se3/Bi2Te3 heterostructure

In spite of much work on topological insulators (TIs), systematic experiments for TI/TI heterostructures remain absent. We grow a high quality heterostructure containing single quintuple layer (QL) of Bi2Se3 on 19 QLs of Bi2Te3 and compare its transport properties with 20 QLs Bi2Se3 and 20 QLs Bi2Te3. All three films are grown on insulating sapphire (0001) substrates by molecular beam epitaxy (MBE). In situ angle-resolved photoemission spectroscopy (ARPES) provides direct evidence that the surface state of 1 QL Bi2Se3 / 19 QLs Bi2Te3 heterostructure is similar to the surface state of the 20 QLs Bi2Se3 and different with that of the 20 QLs Bi2Te3. In ex situ transport measurements, the observed linear magnetoresistance (MR) and weak antilocalization (WAL) of the hybrid heterostructure are similar to that of the pure Bi2Se3 film and not the Bi2Te3 film. This suggests that the single Bi2Se3 QL layer on top of 19 QLs Bi2Te3 dominates its transport properties.

cond-mat.mes-hall↗

arXiv2013

Efficient spectral hole-burning and atomic frequency comb storage in Nd3+:YLiF4

We present spectral hole-burning measurements of the $^{4}I_{9/2}\rightarrow{}^4F_{3/2}$ transition in Nd$^{3+}$:YLiF$_4$. The isotope shifts of Nd$^{3+}$ can be directly resolved in the optical absorption spectrum. We report atomic frequency comb storage with an echo efficiency of up to 35% and a memory bandwidth of 60 MHz in this material. The interesting properties show the potential of this material for use in both quantum and classical information processing.

quant-ph↗

arXiv2013

Which percentile-based approach should be preferred for calculating normalized citation impact values? An empirical comparison of five approaches including a newly developed citation-rank approach (P100)

Percentile-based approaches have been proposed as a non-parametric alternative to parametric central-tendency statistics to normalize observed citation counts. Percentiles are based on an ordered set of citation counts in a reference set, whereby the fraction of papers at or below the citation counts of a focal paper is used as an indicator for its relative citation impact in the set. In this study, we pursue two related objectives: (1) although different percentile-based approaches have been developed, an approach is hitherto missing that satisfies a number of criteria such as scaling of the percentile ranks from zero (all other papers perform better) to 100 (all other papers perform worse), and solving the problem with tied citation ranks unambiguously. We introduce a new citation-rank approach having these properties, namely P100. (2) We compare the reliability of P100 empirically with other percentile-based approaches, such as the approaches developed by the SCImago group, the Centre for Science and Technology Studies (CWTS), and Thomson Reuters (InCites), using all papers published in 1980 in Thomson Reuters Web of Science (WoS). How accurately can the different approaches predict the long-term citation impact in 2010 (in year 31) using citation impact measured in previous time windows (years 1 to 30)? The comparison of the approaches shows that the method used by InCites overestimates citation impact (because of using the highest percentile rank when papers are assigned to more than a single subject category) whereas the SCImago indicator shows higher power in predicting the long-term citation impact on the basis of citation rates in early years. Since the results show a disadvantage in this predictive ability for P100 against the other approaches, there is still room for further improvements.

cs.DL↗

arXiv2013

Harnack Inequalities for Stochastic Equations Driven by Lévy Noise

By using coupling argument and regularization approximations of the underlying subordinator, dimension-free Harnack inequalities are established for a class of stochastic equations driven by a Lévy noise containing a subordinate Brownian motion. The Harnack inequalities are new even for linear equations driven by Lévy noise, and the gradient estimate implied by our log-Harnack inequality considerably generalizes some recent results on gradient estimates and coupling properties derived for Lévy processes or linear equations driven by Lévy noise. The main results are also extended to semi-linear stochastic equations in Hilbert spaces.

math.PR↗

arXiv2013

Drop-port study of microresonator frequency combs: power transfer and time-domain characterization

We use a drop-port geometry to study power transfer in silicon nitride on-chip microresonator frequency comb generators. In sharp contrast with the traditional transmission geometry, we observe smooth output spectra with comparable powers in the pump and adjacent comb lines. An observation of saturation in the drop-port output power is explained semi-empirically by introducing pump saturation into a coupling of modes model. Autocorrelation measurements are performed on the drop-port output, without the need to filter out or suppress the strong pump line as is necessary in thru-port experiments. Passively mode-locked pulses are observed with a normal dispersion microcavity.

physics.optics↗

arXiv2013

Threshold resummation effects in Higgs boson pair production at the LHC

We investigate the resummation effects in the Standard Model Higgs boson pair production through gluon-gluon fusion at the LHC with soft-collinear effective theory. We calculate the total cross section and the invariant mass distribution at Next-to-Next-to-Leading-Logarithmic level with $π^2$-enhanced terms resummed, which are matched to the QCD Next-to-Leading Order results. In the high order QCD predictions exact top quark mass effects are included in full form factors. Our results show that the resummation effects increase the Next-to-Leading Order results by about $20% \sim 30%$, and the scale uncertainty is reduced to 8%, which lead to increased confidence on the theoretical predictions. The PDF+$\as$ uncertainties are almost not changed after including resummation effects. We also study the sensitivities of the total cross section and the invariant mass distribution to the Higgs boson self-coupling. We find that the total cross section and the invariant mass distribution shape depend strongly on the Higgs boson self-coupling, and therefore it is possible to extract Higgs boson self-coupling from the total cross section and invariant mass distribution when the measurement precision increases at the LHC.

hep-ph↗

arXiv2013

Functional inequalities for Nonlocal Dirichlet Forms With Finite Range Jumps or Large Jumps

The paper is a continuation of our paper [12,2], and it studies functional inequalities for non-local Dirichlet forms with finite range jumps or large jumps. Let $α\in(0,2)$ and $μ_V(dx)=C_Ve^{-V(x)}\,dx$ be a probability measure. We present explicit and sharp criteria for the Poincaré inequality and the super Poincaré inequality of the following non-local Dirichlet form with finite range jump $$\mathscr{E}_{α, V}(f,f):= (1/2)\iint_{|x-y|\le 1}\frac{(f(x)-f(y))^2}{|x-y|^{d+α}} dy μ_V(dx);$$ on the other hand, we give sharp criteria for the Poincaré inequality of the non-local Dirichlet form with large jump as follows $$\mathscr{D}_{α, V}(f,f):= (1/2)\iint_{|x-y|> 1}\frac{(f(x)-f(y))^2}{|x-y|^{d+α}} dy μ_V(dx),$$ and also derive that the super Poincaré inequality does not hold for $\mathscr{D}_{α, V}$. To obtain these results above, some new approaches and ideas completely different from \cite{WW, CW} are required, e.g. local Poincaré inequality for $\mathscr{E}_{α, V}$ and $\mathscr{D}_{α, V}$, and the Lyapunov condition for $\mathscr{E}_{α, V}$. In particular, the results about $\mathscr{E}_{α, V}$ show that the probability measure fulfilling Poincaré inequality and super Poincaré inequality for non-local Dirichlet form with finite range jump and that for local Dirichlet form enjoy some similar properties; on the other hand, the assertions for $\mathscr{D}_{α, V}$ indicate that even if functional inequalities for non-local Dirichlet form heavily depend on the density of large jump in the associated Lévy measure, the corresponding small jump plays an important role for local super Poincaré inequality, which is inevitable to derive super Poincaré inequality.

math.PR↗

arXiv2013

A Simple Approach to Functional Inequalities for Non-local Dirichlet Forms

With direct and simple proofs, we establish Poincaré type inequalities (including Poincaré inequalities, weak Poincaré inequalities and super Poincaré inequalities), entropy inequalities and Beckner-type inequalities for non-local Dirichlet forms. The proofs are efficient for non-local Dirichlet forms with general jump kernel, and also work for $L^p (p>1)$ settings. Our results yield a new sufficient condition for fractional Poincaré inequalities, which were recently studied in \cite{MRS,Gre}. To our knowledge this is the first result providing entropy inequalities and Beckner-type inequalities for measures more general than Lévy measures.

math.PR↗

arXiv2013

Experimental unconditionally secure bit commitment

Bit commitment is a fundamental cryptographic task that guarantees a secure commitment between two mutually mistrustful parties and is a building block for many cryptographic primitives, including coin tossing, zero-knowledge proofs, oblivious transfer and secure two-party computation. Unconditionally secure bit commitment was thought to be impossible until recent theoretical protocols that combine quantum mechanics and relativity were shown to elude previous impossibility proofs. Here we implement such a bit commitment protocol. In the experiment, the committer performs quantum measurements using two quantum key distribution systems and the results are transmitted via free-space optical communication to two agents separated with more than 20 km. The security of the protocol relies on the properties of quantum information and relativity theory. We show that, in each run of the experiment, a bit is successfully committed with less than 5.68*10^-2 cheating probability. Our result demonstrates unconditionally secure bit commitment and the experimental feasibility of relativistic quantum communication.

quant-ph↗

arXiv2013

Switching from Crossed Andreev Reflection to Electron Teleportation via Quantum dot

We study electron transport through a normal lead-quantum dot-topological superconductor-quantum dot-normal lead (N-QD-TS-QD-N) junction. Due to the non-local nature of Majorana fermions (MFs) in the topological superconductor, there are two types of single electron transport processes in the junction: crossed Andreev reflection (CAR) and electron teleportation (ET). When the coupling energy of MFs is much larger than the coupling between MFs and QDs, electron can tunnel through topological superconductor either via CAR or ET depending on the energy levels of QDs. For instance, when both energies of QDs (labeled as $ε_1$ and $ε_2$) are equal to the coupling energy of MFs (denoted as $E_M$), the electron in the left lead can teleport to the right lead via MFs while when $ε_1=-ε_2=E_M$ is satisfied, the electron in the left lead can combine one electron in the right lead to form a cooper pair and tunnel into the topological superconductor via MFs. Since both electron teleportation and crossed Andreev reflection manifest the non-local properties of MFs, they can be used to examine the nature of MFs.

cond-mat.mes-hall↗

arXiv2013

Conductance fluctuation and shot noise in disordered graphene systems, a perturbation expansion approach

We report the investigation of conductance fluctuation and shot noise in disordered graphene systems with two kinds of disorder, Anderson type impurities and random dopants. To avoid the brute-force calculation which is time consuming and impractical at low doping concentration, we develop an expansion method based on the coherent potential approximation (CPA) to calculate the average of four Green's functions and the results are obtained by truncating the expansion up to 6th order in terms of "single-site-T-matrix". Since our expansion is with respect to "single-site-T-matrix" instead of disorder strength $W$, good result can be obtained at 6th order for finite $W$. We benchmark our results against brute-force method on disordered graphene systems as well as the two dimensional square lattice model systems for both Anderson disorder and the random doping. The results show that in the regime where the disorder strength $W$ is small or the doping concentration is low, our results agree well with the results obtained from the brute-force method. Specifically, for the graphene system with Anderson impurities, our results for conductance fluctuation show good agreement for $W$ up to $0.4t$, where $t$ is the hopping energy. While for average shot noise, the results are good for $W$ up to $0.2t$. When the graphene system is doped with low concentration 1%, the conductance fluctuation and shot noise agrees with brute-force results for large $W$ which is comparable to the hopping energy $t$. At large doping concentration 10%, good agreement can be reached for conductance fluctuation and shot noise for $W$ up to $0.4t$. We have also tested our formalism on square lattice with similar results. Our formalism can be easily combined with linear muffin-tin orbital first-principles transport calculations for light doping nano-scaled systems, making prediction on variability of nano-devices.

cond-mat.mes-hall↗

arXiv2013

Transport Properties of Topological Insulators Films and Nanowires

The last several years have witnessed the rapid developments in the study and understanding of topological insulators. In this review, after a brief summary of the history of topological insulators, we focus on the recent progress made in transport experiments on topological insulator films and nanowires. Some quantum phenomena, including the weak antilocalization, the Aharonov Bohm effect and the Shubnikov de Haas oscillations, observed in these nanostructures are described. In addition, the electronic transport evidence of the superconducting proximity effect as well as an anomalous resistance enhancement in topological insulator/superconductor hybrid structures is included.

cond-mat.mes-hall↗

arXiv2013

A Ni-Fe Layered Double Hydroxide-Carbon Nanotube Complex for Water Oxidation

Highly active, durable and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions including water splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel iron layered double hydroxide nanoplates on mildly oxidized multi-walled carbon nanotubes. Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-layered double hydroxide. The nanoplates were covalently attached to a network of nanotubes, affording excellent electrical wiring to the nanoplates. The ultra-thin Ni-Fe layered double hydroxide nanoplates/carbon nanotube complex was found to exhibit unusually high electro-catalytic activity and stability for oxygen evolution and outperformed commercial precious metal Ir catalysts.

physics.chem-ph↗

arXiv2013

Searching for the signal of dark matter and photon associated production at the LHC beyond leading order

We study the signal of dark matter and photon associated production induced by the vector and axial-vector operators at the LHC, including the QCD next-to-leading order (NLO) effects. We find that the QCD NLO corrections reduce the dependence of the total cross sections on the factorization and renormalization scales, and the $K$ factors increase with the increasing of the dark matter mass, which can be as large as about 1.3 for both the vector and axial-vector operators. Using our QCD NLO results, we improve the constraints on the new physics scale from the results of the recent CMS experiment. Moreover, we show the Monte Carlo simulation results for detecting the $γ+\Slash{E}_{T}$ signal at the QCD NLO level, and present the integrated luminosity needed for a $5σ$ discovery at the 14 TeV LHC . If the signal is not observed, the lower limit on the new physics scale can be set.

hep-ph↗

arXiv2013

Functional Inequalities for Stable-Like Dirichlet Forms

Let $V\in C^2(\R^d)$ such that $μ_V(\d x):= \e^{-V(x)}\,\d x$ is a probability measure, and let $å\in (0,2)$. Explicit criteria are presented for the $å$-stable-like Dirichlet form $$\E_{å,V}(f,f):= \int_{\R^d\times\R^d} \ff{|f(x)-f(y)|^2}{|x-y|^{d+α}}\,\d y\,\e^{-V(x)}\,\d x$$ to satisfy Poincaré-type (i.e., Poincaré, weak Poincaré and super Poincaré) inequalities. As applications, sharp functional inequalities are derived for the Dirichlet form with $V$ having some typical growths. Finally, the main result of \cite{MRS} on the Poincaré inequality is strengthened

math.PR↗