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Jian Zhou

Publications and source records attributed to Jian Zhou.

At least 235 records · Page 13Linked to original sources
arXiv2018

Exotic Node Line in ternary MgSrSi-type crystals

Node line (NL) band-touchings protected by mirror symmetry (named as $m$-NL), the product of inversion and time reversal symmetry $\mathcal{S=PT}$ ($s$-NL), or nonsymmorphic symmetry are nontrivial topological objects of topological semimetals (SMs) in the Brillouin Zone (BZ). In this work, we screened the family of MgSrSi-type crystals using first principles calculations, and discovered that more than 70 members are NLSMs. A new type of multi-loop structure was found in AsRhTi that a $s$-NL touches robustly with a $m$-NL at some "nexus point", and in the meanwhile a second $m$-NL crosses with the $s$-NL to form a Hopf-link. Unlike the previously proposed Hopf-link formed by two $s$-NLs or two $m$-NLs, a Hopf-link formed by a $s$-NL and a $m$-NL requires a minimal three-band model to characterize its essential electronic structure. The associated topological surface states on different surfaces of AsRhTi crystal were also obtained. Even more complicated and exotic multi-loop structure of NLs were predicted in AsFeNa and PNiNb. Our work may shed light on search for exotic multi-loop NLSMs in real materials.

cond-mat.mtrl-sci↗
arXiv2018

Significant low lattice thermal conductivity and potential high thermoelectric figure of merit in Na$_2$MgSn

Thermoelectric materials enables the harvest of waste heat and directly conversion into electricity. In search of high efficient thermoelectric materials, low thermal conductivity of a material is essential and critical. Here, we have theoretically investigated the lattice thermal conductivity and thermoelectric properties of layered intermetallic Na$_2$MgSn and Na$_2$MgPb based on the density functional theory and linearized Boltzmann equation with the single-mode relaxation-time approximation. It is found that both materials exhibit very low and anisotropic intrinsic lattice thermal conductivity. Despite of the very low mass density and simple crystal structure of Na$_2$MgSn, its lattice thermal conductivities along $a$ and $c$ axes are only 1.75 and 0.80 W/m$\cdot$K respectively at room temperatures. When Sn is replaced by the heavier element Pb, its lattice thermal conductivities decrease remarkably to 0.51 and 0.31 W/m$\cdot$K respectively along $a$ and $c$ axes at room temperatures. We show that the low lattice thermal conductivities of both materials are mainly due to their very short phonon lifetimes, which are roughly between 0.4 to 4.5 ps. Combined with previous experimental measurements, the metallic Na$_2$MgPb can not be a good thermoelectric material. However, we predict that the semiconducting Na$_2$MgSn is a potential room-temperature thermoelectric material with a considerable $ZT$ of 0.34 at 300 K. Our calculations not only imply that the intermetallic Na$_2$MgSn is a potential thermoelectric material, but also can motivate more theoretical and experimental works on the thermoelectric researches in simple layered intermetallic compounds.

cond-mat.mtrl-sci↗
arXiv2018

Resumming subleading Sudakov logarithms in saturation regime

We investigate the scale dependence of transverse momentum dependent(TMD) gluon distribution in saturation regime. We found that in the Collins-2011 scheme, the scale dependence of small x gluon TMD is governed by the same renormalization group(RG) equation that holds at moderate or large $x$. Following the standard procedure, one then can resum both double leading logarithm and single leading logarithm in saturation regime by jointly solving the Collins-Soper equation and the RG equation.

hep-ph↗
arXiv2018

Experimental evidence of giant chiral magnetic effect in type-II Weyl semimetal WP$_{2+δ}$ crystals

Chiral magnetic effect is a quantum phenomenon that is breaking of chiral symmetry of relativistic Weyl fermions by quantum fluctuation under paralleled electric field E and magnetic field B. Intuitively, Weyl fermions with different chirality, under stimulus of paralleled E and B, will have different chemical potential that gives rise to an extra current, whose role likes a chiral battery in solids. However, up to now, the experimental evidence for chiral magnetic effect is the negative longitudinal magnetoresistance rather than a chiral electric source. Here, totally different from previous reports, we observed the giant chiral magnetic effect evidenced by: 'negative' resistivity and corresponding voltage-current curves lying the second-fourth quadrant in type-II Weyl semimetal WP$_{2+δ}$ under following conditions: the misaligned angle between E and B is smaller than 20$^\circ$, temperature <30 K and externally applied E<50 mA. Phenomenologically, based on macroscopic Chern-Simon-Maxwell equation, the giant chiral magnetic effect observed in WP$_{2+δ}$ is attributed to two-order higher coherent time of chiral Weyl-fermion quantum state over Drude transport relaxation-time. This work demonstrates the giant chiral-magnetic/chiral-battery effect in Weyl semimetals.

cond-mat.mtrl-sci↗
arXiv2018

Sea quark Sivers distribution

We compute sea quark Sivers distribution within color glass condensate(CGC) framework. It has been found that up to the leading logarithm accuracy, the collinear twist-3 approach and the CGC calculation yield the same result for sea quark Sivers distribution in the dilute limit. We further verify that transverse momentum dependent factorization is consistent with CGC treatment at small $x$ for the case of transverse spin asymmetry in open charm quark production in semi-inclusive deeply inelastic scattering process in an overlap kinematical region.

hep-ph↗
arXiv2018

K-Theory of Hilbert Schemes as a Formal Quantum Field Theory

We define a notion of formal quantum field theory and associate a formal quantum field theory to K-theoretical intersection theories on Hilbert schemes of points on algebraic surfaces. This enables us to find an effective way to compute K-theoretical intersection theories on Hilbert schemes via a connection to Macdonald polynomials and vertex operators.

math.AG↗
arXiv2018

Exclusive double quarkonium production and generalized TMDs of gluons

Being the "mother distributions" of all types of two-parton correlation functions, generalized transverse momentum dependent parton distributions (GTMDs) have attracted a lot of attention over the last years. We argue that exclusive double production of pseudoscalar quarkonia ($η_c$ or $η_b$) in nucleon-nucleon collisions gives access to GTMDs of gluons.

hep-ph↗
arXiv2018

Computational experiments successfully predict the emergence of autocorrelations in ultra-high-frequency stock returns

Social and economic systems are complex adaptive systems, in which heterogenous agents interact and evolve in a self-organized manner, and macroscopic laws emerge from microscopic properties. To understand the behaviors of complex systems, computational experiments based on physical and mathematical models provide a useful tools. Here, we perform computational experiments using a phenomenological order-driven model called the modified Mike-Farmer (MMF) to predict the impacts of order flows on the autocorrelations in ultra-high-frequency returns, quantified by Hurst index $H_r$. Three possible determinants embedded in the MMF model are investigated, including the Hurst index $H_s$ of order directions, the Hurst index $H_x$ and the power-law tail index $α_x$ of the relative prices of placed orders. The computational experiments predict that $H_r$ is negatively correlated with $α_x$ and $H_x$ and positively correlated with $H_s$. In addition, the values of $α_x$ and $H_x$ have negligible impacts on $H_r$, whereas $H_s$ exhibits a dominating impact on $H_r$. The predictions of the MMF model on the dependence of $H_r$ upon $H_s$ and $H_x$ are verified by the empirical results obtained from the order flow data of 43 Chinese stocks.

q-fin.TR↗
arXiv2018

On Quasimodularity of Some Equivariant Intersection Numbers on the Hilbert Schemes

We observe that certain equivariant intersection numbers of Chern characters of tautological sheaves on Hilbert schemes for suitable circle actions can be computed using the Bloch-Okounkov formula, hence they are related to Gromov-Witten invariants of elliptic curves and its operator formalism in terms of operators on the Fock space.

math.AG↗
arXiv2018

Standing waves for quasilinear Schröinger equations with indefinite potentials

We consider quasilinear Schrödinger equations in $\mathbb{R}^{N}$ of the form% \[ -Δu+V(x)u-uΔ(u^{2})=g(u)\text{,}% \] where $g(u)$ is $4$-superlinear. Unlike all known results in the literature, the Schrödinger operator $-Δ+V$ is allowed to be indefinite, hence the variational functional does not satisfy the mountain pass geometry. By a local linking argument and Morse theory, we obtain a nontrivial solution for the problem. In case that $g$ is odd, we get an unbounded sequence of solutions.

math.AP↗
arXiv2017

Security of Continuous-Variable Quantum Key Distribution with Discrete Modulation against General Attacks

We provide a security analysis of continuous-variable quantum key distribution (CVQKD) with discrete modulation against general attacks in a realistic finite-size regime. To realize this goal, we first prove security of the continuous-variable quantum key distribution protocol with discrete modulation against collective attacks by using the reliable tomography of the covariance matrix, leading to the reliable and tight error bounds in the derived confidence regions. Combining the proof with de Finetti reduction, the discrete-modulation-based continuous-variable quantum key distribution (DM-CVQKD) is proved to be secure even exposing to general attacks. Specially, we use an energy test to truncate the Hilbert space globally to provide security.

quant-ph↗
arXiv2017

A Distributed Parallel Model to Analyze Journal Impact Factors

A simple abstract model is developed as a parallel experimental basis for the aim of exploring the differences of journal impact factors, particularly between different disciplines. Our model endeavors to simulate the publication and citation behaviors of the articles in the journals belonging to a similar discipline, in a distributed manner. Based on simulation experiments, the mechanism of influence from several fundamental factors to the trend of impact factor is revealed. These factors include the average review cycle, average number of references and yearly distribution of references. Moreover, satisfactory approximation could possibly be observed between certain actual data and simulation results.

cs.DL↗
arXiv2017

Fast holonomic quantum computation based on solid-state spins with all-optical control

Holonomic quantum computation is a quantum computation strategy that promises some built-in noise-resilience features. Here, we propose a scheme for nonadiabatic holonomic quantum computation with nitrogen-vacancy center electron spins, which are characterized by fast quantum gates and long qubit coherence times. By varying the detuning, amplitudes, and phase difference of lasers applied to a nitrogen-vacancy center, one can directly realize an arbitrary single-qubit holonomic gate on the spin. Meanwhile, with the help of cavity-assisted interactions, a nontrivial two-qubit holonomic quantum gate can also be induced. The distinct merit of this scheme is that all the quantum gates are obtained via an all-optical geometric manipulation of the solid-state spins. Therefore, our scheme opens the possibility for robust quantum computation using solid-state spins in an all-optical way.

quant-ph↗
arXiv2017

On Geometry and Symmetry of Kepler Systems. I

We study the Kepler metrics on Kepler manifolds from the point of view of Sasakian geometry and Hessian geometry. This establishes a link between the problem of classical gravity and the modern geometric methods in the study of AdS/CFT correspondence in string theory.

math-ph↗
arXiv2017

Origin of the abnormal diffusion of transition metal in rutile

Diffusion of dopants in rutile is the fundamental process that determines the performance of many devices in which rutile is used. The diffusion behavior is known to be highly sample-dependent, but the reasons for this are less well understood. Here, rutile is studied by using first-principles calculations, in order to unravel the microscopic origins of the diverse diffusion behaviors for different doping elements. Anomalous diffusion behavior in the open channel along [001] direction is found: larger atoms include Sc and Zr have lower energy barrier for diffusion via interstitial mechanism, apparently contradicting their known slow diffusion rate. To resolve this, we present an alternate model for the overall diffusion rate of the large-size dopants in rutile, showing that parallel to the [001] channel, it is limited by the formation of the interstitial states, whereas in the direction perpendicular to [001], it proceeds via a kick-out mechanism. By contrast, Co and Ni, prefer to stay in the interstitial site of rutile, and have conventional diffusion with a very small migration barrier in the [001] channel. This leads to highly anisotropic and fast diffusion. The diffusion mechanisms found in the present study can explain the diffusion data measured by experiments, and these findings provide novel understanding for the classic diffusion topic.

cond-mat.mtrl-sci↗
arXiv2017

Polygamy relation for the Rényi-$α$ entanglement of assistance in multi-qubit systems

We prove a new polygamy relation of multi-party quantum entanglement in terms of Rényi-$α$ entanglement of assistance for $\left( {\sqrt 7 - 1} \right)/2\leqα\leq \left( {\sqrt 13 - 1} \right)/2$. This class of polygamy inequality reduces to the polygamy inequality based on entanglement of assistance since Rényi-$α$ entanglement is a generalization of entanglement of formation. We further show that the polygamy inequality also holds for the $μ$th power of Rényi-$α$ entanglement of assistance.

quant-ph↗