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Shi-Jie Xiong

Publications and source records attributed to Shi-Jie Xiong.

35 records · Page 2Linked to original sources
arXiv2007

The process of coevolutionary competitive exclusion: speciation, multifractality and power-laws in correlation

Competitive exclusion, a key principle of ecology, can be generalized to understand many other complex systems. Individuals under surviving pressure tend to be different from others, and correlations among them change correspondingly to the updating of their states. We show with numerical simulation that these aptitudes can contribute to group formation or speciation in social fields. Moreover, they can lead to power-law topological correlations of complex networks. By coupling updating states of nodes with variation of connections in a network, structural properties with power-laws and functions like multifractality, spontaneous ranking and evolutionary branching of node states can emerge out simultaneously from the present self-organized model of coevolutionary process.

physics.data-an↗
arXiv2007

Entropy exchange, coherent information and concurrence

For a simple model we derive analytic expressions of entropy exchange and coherent information, from which relations between them and the concurrence are drawn. We find that in the quantum evolution the entropy exchange exhibits behavior \textsl{opposite} to that of the concurrence, whereas the coherent information shows features very similar to those of the concurrence. The meaning of this result for general systems is discussed.

quant-ph↗
arXiv2007

Entanglement fidelity and measurement of entanglement preserving in quantum processes

The entanglement fidelity provides a measure of how well the entanglement between two subsystems is preserved in a quantum process. By using a simple model we show that in some cases this quantity in its original definition fails in the measurement of the entanglement preserving. On the contrary, the modified entanglement fidelity, obtained by using a proper local unitary transformation on a subsystem, is shown to exhibit the behavior similar to that of the concurrence in the quantum evolution.

quant-ph↗
arXiv2007

Quantum Theory of Spontaneous Emission from Exciton-Electron-Phonon Complex in Solid: Quantum Interference and Many-Body Effect

A full quantum mechanical theory for the spontaneous emission from excitons simultaneously coupled to electronic excitations and anharmonic phonons in solid is developed. Origin of detailed structures, such as zero-phonon line splitting, Fano lineshape near one phonon sideband, strong second-order phonon Stokes line, asymmetric phonon anti-Stokes lines, and two-electron satellites as well as their phonon replicas recently revealed in the low-temperature photoluminescence of ZnO, has been identified by quantitative calculations from the theory.

cond-mat.mtrl-sci↗
arXiv2007

Berry-Phase Induced Dynamical Instability and Minimum Conductivity in Graphene

Single-layer carbon, or graphene, demonstrates amazing transport properties, such as the minimum conductivity near $\frac{4e^2}{h}$ independent of shapes and mobility of samples. This indicates there exist some unusual effects due to specific Dirac dispersion relation of fermion in two dimensions. By deriving fermion-lattice interaction Hamiltonian we show that Berry phases can be produced in fermion states around two Dirac points by relative rotations of two sublattices. The Berry phases in turn remove the degeneracies of energies for states near the Fermi surface, leading to a dynamical instability of the lattice with respect to the rotations. By considering the Berry phases emerging in an uncertain way on fermion wavefunctions in vicinities of the Fermi surface, the conductivity is calculated by using the Landauer-Bütticker formula together with the transfer-matrix technique, verifying $\sim \frac{4e^2}{h}$ quantized minimum conductivity as observed in experiments independent of shapes and sizes. The relationship between the chaotic structure of fermions due to the Berry phases and the classical transport properties are discussed. The physical meaning is profound as this relationship provides an excellent example to elucidate the mechanism of quantum-classical transition.

cond-mat.mes-hall↗
arXiv2005

Phonon Coherence and New Set of Sidebands in Phonon-Assisted Photoluminescence

We investigate excitonic polaron states comprising a local exciton and phonons in the longitudinal optical (LO) mode by solving the Schrödinger equation. We derive an exact expression for the ground state (GS), which includes multi-phonon components with coefficients satisfying the Huang-Rhys factors. The recombination of GS and excited polaron states gives one set of sidebands in photoluminescence (PL): the multi-phonon components in the GS produce the Stokes lines and the zero-phonon components in the excited states produce the anti-Stokes lines. By introducing the mixing of the LO mode and environal phonon modes, the exciton will also couple with the latter, and the resultant polaron states result in another set of phonon sidebands. This set has a zero-phonon line higher and wider than that of the first set due to the tremendous number of the environal modes. The energy spacing between the zero-phonon lines of the first and second sets is proved to be the binding energy of the GS state. The common exciton origin of these two sets can be further verified by a characteristic Fano lineshape induced by the coherence in the mixing of the LO and the environal modes.

cond-mat.mtrl-sci↗
arXiv2005

Excitonic Polaron States and Fano Interference in Phonon-Assisted Photoluminescence of Bound Excitons in ZnO

We report a photoluminescence observation of robust excitonic polarons due to strong coupling of exciton and longitudinal optical (LO) phonon as well as Fano-type interference in high quality ZnO crystal. At low enough temperatures, the strong coupling of excitons and LO phonons leads to not only traditional Stokes lines (SLs) but also up to second-order anti-Stokes lines (ASLs) besides the zero-phonon line (ZPL). The SLs and ASLs are found to be not mirror symmetric with respect to the ZPL, strongly suggesting that they are from different coupling states of exciton and phonons. It is more interesting that a new group of peaks, including a ZPL and several SLs, are observed. The observations can be explained with a newly developed theory in which this group is attributed to the ground excitonic polaron state and the other group is from the excited polaron states with LO phonon components partially decaying into environal phonon modes. Besides these spectral features showing the quasiparticle properties of exciton-phonon coupling system, the first-order SL is found to exhibit characteristic Fano lineshape, caused by quantum interference between the LO components of excitonic polarons and the environal phonons. These findings lead to a new insight into fundamental effects of exciton-phonon interaction.

cond-mat.mtrl-sci↗
arXiv2003

Scaling in directed dynamical small-world networks with random responses

A dynamical model of small-world network, with directed links which describe various correlations in social and natural phenomena, is presented. Random responses of every site to the imput message are introduced to simulate real systems. The interplay of these ingredients results in collective dynamical evolution of a spin-like variable S(t) of the whole network. In the present model, global average spreading length \langel L >_s and average spreading time _s are found to scale as p^-αln N with different exponents. Meanwhile, S behaves in a duple scaling form for N>>N^*: S ~ f(p^-βq^γt'_sc), where p and q are rewiring and external parameters, α, β, γand f(t'_sc) are scaling exponents and universal functions, respectively. Possible applications of the model are discussed.

cond-mat.dis-nn↗
arXiv2001

Localization Transition in Multilayered Disordered Systems

The Anderson delocalization-localization transition is studied in multilayered systems with randomly placed interlayer bonds of density $p$ and strength $t$. In the absence of diagonal disorder (W=0), following an appropriate perturbation expansion, we estimate the mean free paths in the main directions and verify by scaling of the conductance that the states remain extended for any finite $p$, despite the interlayer disorder. In the presence of additional diagonal disorder ($W > 0$) we obtain an Anderson transition with critical disorder $W_c$ and localization length exponent $ν$ independently of the direction. The critical conductance distribution $P_{c}(g)$ varies, however, for the parallel and the perpendicular directions. The results are discussed in connection to disordered anisotropic materials.

cond-mat.dis-nn↗
arXiv2001

Power-law Localization in 2D, 3D with Off-diagonal Disorder

We describe non-conventional localization of the midband E=0 state in square and cubic finite bipartite lattices with off-diagonal disorder by solving numerically the linear equations for the corresponding amplitudes. This state is shown to display multifractal fluctuations, having many sparse peaks, and by scaling the participation ratio we obtain its disorder-dependent fractal dimension $D_{2}$. A logarithmic average correlation function grows as $g(r) \sim η\ln r$ at distance $r$ from the maximum amplitude and is consistent with a typical overall power-law decay $|ψ(r)| \sim r^{-η}$ where $η$ is proportional to the strength of off-diagonal disorder.

cond-mat.dis-nn↗
arXiv2000

Localization-Delocalization Transition of Electron States in a Disordered Quantum Small World Network

We investigate the localization behavior of electrons in a random lattice which is constructed from a quasi-one-dimensional chain with large coordinate number $Z$ and rewired bonds, resembling the small-world network proposed recently but with site-energy disorder and quantum links instead of classical ones. The random rewiring of bonds in the chain with large $Z$ enhances both the topological disorder and the effective dimensionality. From the competition between disorder and dimensionality enhancement a transition from localization to delocalization is found by using the level statistics method combined with the finite-size scaling analysis. The critical value of the rewiring rate for this transition is determined numerically. We obtain a universal critical integrated distribution of level spacing $s$ in the form $I_{p_{c}}(s)\propto \exp (-A_{c}s^α)$, with $A_{c}\simeq 1.50$ and $α\simeq 1.0$. This reveals the possible existence of metal-insulator transition in materials with chains as the backbones.

cond-mat.dis-nn↗
arXiv1999

Transport properties of the hierarchical model for stretched polymers

We prove that the hierarchical fractal model recently proposed for describing the stretched polymers [A. N. Samukhin et al, Phys. Rev. Lett.{\bf 78}, 326(1997)] is equivalent to a one-dimensional chain with hierarchical aperiodic structure. By use of the transfer matrix technique we calculate the electronic transmission and the dc conductance. We find that there exist sharp-edged transmission subbands and gaps, but the transmission subbands are rich in substructures which show self-similarity. The temperature dependence of conductance $g (T)$ is sensitive to the variation of the Fermi level and to the structure parameters $m$ and $n$ of the original fractal structure. The relationship of the obtained results to the experimental data and other theoretical works is discussed.

cond-mat.dis-nn↗
arXiv1998

One-Dimensional Extended States in Partially Disordered Planar Systems

We obtain analytically a continuum of one-dimensional ballistic extended states in a two-dimensional disordered system, which consists of compactly coupled random and pure square lattices. The extended states give a marginal metallic phase with finite conductivity $σ_{0}=2e^2/h$ in a wide energy range, whose boundaries define the mobility edges of a first-order metal-insulator transition. We show current-voltage duality, $H_{\parallel}/T$ scaling of the conductivity in parallel magnetic field $H_{\parallel}$ and non-Fermi liquid properties when long-range electron-electron interactions are included.

cond-mat.dis-nn↗
arXiv1997

Anisotropic Quantum Transport in Layered High--$T_c$ Cuprates

A random lattice model with dilute interlayer bonds of density $p$ is proposed to describe the underdoped high--$T_c$ cuprates. We show analytically via an appropriate perturbation expansion and verify independently by numerical scaling of the conductance that for any finite $p$ the states remain extended in all directions, despite the presence of interlayer disorder. However, the obtained electronic transport is highly anisotropic with violent conductance fluctuations occuring in the layering direction, which can be responsible for the experimentally observed metallic "in-plane" and semiconducting "out-of-plane" resistivity of the cuprates.

cond-mat.dis-nn↗
arXiv1997

Sparse random matrix configurations for two or three interacting electrons in a random potential

We investigate the random matrix configurations for two or three interacting electrons in one-dimensional disordered systems. In a suitable non-interacting localized electron basis we obtain a sparse random matrix with very long tails which is different from a superimposed random band matrix usually thought to be valid. The number of non-zero off-diagonal matrix elements is shown to decay very weakly from the matrix diagonal and the non-zero matrix elements are distributed according to a Lorentzian around zero with also very weakly decaying parameters. The corresponding random matrix for three interacting electrons is similar but even more sparse.

cond-mat.dis-nn↗
arXiv1997

Magnetoquantum Oscillations in Mesoscopic Multi-Channel Rings

We obtain exact analytical expressions for the electronic transport through a multi-channel system, also with an applied magnetic field. The geometrical structure of the electrodes is found to cause a splitting of the conduction band into many subbands, depending on the number and the length of the chains and the conductance approaches zero when the chain number is sufficiently large, due to quantum interference. In the presence of a magnetic field a very complicated oscillatory behavior of the conductance is found with a very sensitive dependence on the number of chains and their lengths, in a remarkable distinction from the usual oscillations in two-channel Aharonov-Bohm (AB) rings. In the multi-channel system the obtained oscillation patterns and their periodicities depend on the partitioning of the magnetic flux in the areas enclosed by the electronic paths. The present study may provide a useful information for quantum dots with a special configuration.

cond-mat.mes-hall↗