Existence and Stability of Two-Dimensional Compact-Like Discrete Breathers in Discrete Two-Dimensional Monatomic Square Lattices

Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generalized discrete two-dimensional monatomic model. It is proven that the two- dimensional compact-like discrete breathers exist not only in two-dimensional soft Φ4 potentials but also in hard two-dimensional Φ4 potentials and pure two-dimensional K4 lattices. The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Φ4 potential are determined by coupling parameter K4, while those in pure two-dimensional K4 lattices have no coupling with parameter K4. The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.     

Fabrication of Two-Dimensional Organic Photonic Crystal Microcavity

A two-dimensional polystyrene photonic crystal microcavity is fabricated by the method ot tocused ion Oeam etching. The scanning electron microscopy and the transmittance spectrum are used to characterize the properties of the photonic crystal microcavity. The quality factor and the transmittance of the photonic crystal microcavity is more than 530 and 90%, respectively. The measured results are in agreement with the theoretical predictions.     

Non-Achievability of Metal-Insulator Transition in Two-Dimensional Systems

We present a simple demonstration of the nonfeasibility of metal-insulator transition in an exactly two-dimensional （2D） system. The Hartree-Fock potential in the 3D system is suitably modified and presented for the 2D case. The many body effects are included in the screening function, and binding energies of a donor are obtained as a function of impurity concentration so as to find out the possible way leading metal-insulator transition in the 2D system. While solving for the binding energy for a shallow donor in an isolated well of a GaAs/Ga1-x Als As superlattice system within the effective mass approximation, it leads to unphysical results for higher concentrations. It shows that the phase transition, the bound electron entering into the conduction band whereby （H）min=0, is not possible beyond this concentration. The results suggest thai a phase transition is impossible in 213 systems, supporting the scaling theory of localization. The results are compared with the existing data available and discussed in the light of existing literature.     

Dynamic Phase Transition of Two-Dimensional Disordered Colloids

Using Langevin simulations, we numerically study the influence of temperature to the dynamics of driven two-dimensional colloids on a disordered substrate. With decreasing temperature, the result shows a dynamic phase transition from the moving liquid to the moving smectic at high driving forces. A peak appears in the dynamically-critical driving force across the transition, accompanied by a clear cross of the curves of velocity-force dependence.     

Bessel-Modal Method for Finite-Height Two-Dimensional Photonic Crystal

By applying the dyadic Green function, the dispersion relation of two-dimensional photonic crystal can be expressed as the cylindrical wave expansions of eigenmodes. With the aid of Green‘s theorem, the plane-wave coefficients of eigenmodes are reconstructed and employed to formulate the scattering matrix of finite-height twodimensional photonic crystal. These operations make the convergence rate very rapid, and reduce the dimension of the scattering matrix. As a demonstration, we present the transmission and electromagnetic field distributions for an InGaAsIn photonic crystal, and investigate their convergence.     

A Lattice Boltzmann Model for Two-Dimensional Magnetohydrodynamics

A lattice Boltzmann model （LBM） has been developed for simulating magnetohydrodynamics （MHD） along the line of Dellar [J. Comput. Phys. 179 （2002）95]. In this model the magnetic field is presented by a vector valued magnetic distribution function which obeys a vector Boltzmann equation. The truncated error of the equilibrium distribution in the present model is up to order O（u^4） in velocity u rather than the usual 0（u^3）. For verification, the model is applied to solve the shock tube problem and the main features of the flow predicted by the model are found to compare well with the corresponding results obtained with high-order semi-discrete schemes [J. Comput. Phys. 201 （2004） 261]. The numerical experiments have also shown that the present LBM model with the equilibrium distribution truncated at O（u^4） performs much better in terms of numerical stability than those truncated at O（u^3）.     

Absolute Gap of Two-Dimensional Fractal Photonic Structure

We propose a model for two-dimensional photonic materials constructed on a kind of fractal structures. Total energy flows of the photonic materials constructed with either dielectric cylinders or air holes show that both of them possess absolute gaps for the electromagnetic waves.     

Discrete Holomorphicity at Two-Dimensional Critical Points

After a brief review of the historical role of analyticity in the study of critical phenomena, an account is given of recent discoveries of discretely holomorphic observables in critical two-dimensional lattice models. These are objects whose correlation functions satisfy a discrete version of the Cauchy-Riemann relations. Their existence appears to have a deep relation with the integrability of the model, and they are presumably the lattice versions of the truly holomorphic observables appearing in the conformal field theory (CFT) describing the continuum limit. This hypothesis sheds light on the connection between CFT and integrability, and, if verified, can also be used to prove that the scaling limit of certain discrete curves in these models is described by Schramm-Loewner evolution (SLE).     

Fabrication of a Two-Dimensional Organic Photonic Crystal

A high-quality two-dimensional polystyrene photonic crystal is fabricated by the method of focused ion beam etching. The scanning electron microscopy (SEM) and the transmittance spectrum are used to characterize the properties of the photonic crystal. The measured transmittance spectrum is in agreement with the theoretical one. The influences of the disorders caused by the random perturbations in the diameter or the position of the air holes on the photonic band structure are analysed. It is found that the phtonic bandgap can tolerate less than 10% degree of disorder.     

Two-Dimensional Breather Lattice Solutions and Compact-Like Discrete Breathers and Their Stability in Discrete Two-Dimensional Monatomic β-FPU Lattice

We restrict our attention to the discrete two-dimensional monatomic β-FPU lattice. We look for two- dimensional breather lattice solutions and two-dimensional compact-like discrete breathers by using trying method and analyze their stability by using Aubry＇s linearly stable theory. We obtain the conditions of existence and stability of two-dimensional breather lattice solutions and two-dimensional compact-like discrete breathers in the discrete two- dimensional monatomic β-FPU lattice.     

Ferroelectricity and Large Rashba Splitting in Two-Dimensional Tellurium

Two-dimensional(2D) ferroelectric(FE) systems are promising candidates for non-volatile nanodevices.Previous studies mainly focused on 2D compounds.Though counter-intuitive,here we propose several new phases of tellurium with(anti)ferroelectricity.Two-dimensional films can be viewed as a collection of one-dimensional chains,and lone-pair instability is responsible for the(anti)ferroelectricity.The total polarization is determined to be 0.34×10^-10C/m for the FE ground state.Due to the ...     

Homogenization of Two-Dimensional Phononic Crystals at Low Frequencies

Effective velocities of elastic waves propagating in two-dimensional phononic crystal at low frequencies are analysed theoretically, and exact analytical formulas for effective velocities of elastic waves are derived according to the method presented by Krokhin et al. [Phys. Rev. Lett. 91 （2003） 264302]. Numerical calculations for phononic crystals consisted of array of Pb cylinders emSedded in epoxy show that the composites have distinct anisotropy at low filling fraction. The anisotropy increases as the filling fraction increases, while as the filling fraction closes to the limitation, the anisotropy decreases.     

Magnetic Phase Transition in Strained Two-Dimensional CrSeTe Monolayer

Tunable magnetic phase transition in two-dimensional materials is a fascinating subject of research. We perform first-principle calculations based on density functional theory to clarify the magnetic property of CrSeTe monolayer modulated by the biaxial compressive strain. Based on the stable structure confirmed by the phonon calculation, CrSeTe is determined to be a ferromagnetic metal that undergoes a phase transition from a ferromagnetic state to an antiferromagnetic state with nearly 2.75% c...     

Two-Dimensional （2D） Polygonal Electromagnetic Cloaks

Transformation optics offers remarkable control over electromagnetic fields and opens an exciting gateway to design ＇invisible cloak devices＇ recently. We present an important class of two-dimensional （2D） cloaks with polygon geometries. Explicit expressions of transformed medium parameters are derived with their unique properties investigated. It is found that the elements of diagonalized permittivity tensors are always positive within an irregular polygon cloak besides one element diverges to plus infinity and the other two become zero at the inner boundary. At most positions, the principle axes of permittivity tensors do not align with position vectors. An irregular polygon cloak is designed and its invisibility to external electromagnetic waves is numerically verified. Since polygon cloaks can be tailored to resemble any objects, the transformation is finally generalized to the realization of 2D cloaks with arbitrary geometries.     

Two-Dimensional One-Component Plasma on Flamm’s Paraboloid

We study the classical non-relativistic two-dimensional one-component plasma at Coulomb coupling Γ=2 on the Riemannian surface known as Flamm’s paraboloid which is obtained from the spatial part of the Schwarzschild metric. At this special value of the coupling constant, the statistical mechanics of the system are exactly solvable analytically. The Helmholtz free energy asymptotic expansion for the large system has been found. The density of the plasma, in the thermodynamic limit, has been carefully studied in various situations.     

Two-Dimensional Thermal Regulation Based on Non-Hermitian Skin Effect

The non-Hermitian skin effect has been applied in multiple fields. However, there are relatively few models in the field of thermal diffusion that utilize the non-Hermitian skin effect for achieving thermal regulation. Here, we propose two non-Hermitian Su–Schrieffer–Heeger(SSH) models for thermal regulation: one capable of achieving edge states, and the other capable of achieving corner states within the thermal field. By analyzing the energy band structures and the generalized Brillouin zone, ...     

Two-Dimensional Photonic Band-Gap Defect Modes with Deformed Lattice

A numerical study of the defect modes in two-dimensional photonic crystals with deformed triangular lattice is presented by using the supercell method and the finite-difference time-domain method. We find the stretch or shrink of the lattice can bring the change not only on the frequencies of the defect modes but also on their magnetic field distributions. We obtain the separation of the doubly degenerate dipole modes with the change of the lattice and find that both the stretch and the shrink of the lattice can make the dipole modes separate large enough to realize the single-mode emission. These results may be advantageous to the manufacture of photonic crystal lasers and provide a new way to realize the single-mode operation in photonic crystal lasers.     

Interaction between Two-Dimensional White-Light Photovoltaic Dark Spatial Solitons

Using fully incoherent white light emitted from an incandescent bulb （a line source） and amplitude mask, we study experimentally the interaction between two 21） white-light photovoltaic dark spatial solitons with three different separations （40μm, 50μm and 60μm） and arrangement directions （parallel to, perpendicular to and tilted at 45° with respect to the crystalline c axis） propagating in parallel in close proximity in seff-defocusing LiNbO3：Fe crystal. Experimental results reveal that a 21） white-light dark soliton pair only experiences attractive forces when their mutual separation is sufflciently small （〈 60 μm）, and the degree of the attraction depends on their mutual separation and their arrangement direction. When the separation is larger than 60 μm, the interaction is not evident.     

Nonmean-Field Model for Ostwald Ripening of Two-Dimensional Islands

A nonmean-field model for the ripening of two-dimensional islands is presented. In this model, the adatom sea is divided into many small cells that are the polygons of a Voronoi network. The chemical potentials of adatom seas surrounding different islands are different. Strain generated by lattice mismatch is introduced into the model.Computer simulation under periodic boundary conditions is carried out to describe the island ripening in two cases (with and without strain), and demonstrates that small islands may grow faster than large islands, which cannot occur in the mean-field model. The simulated results also show that including strain will slow down the evolution of average island size, and an explanation for this is given.     

Experimental Demonstration of Two-Dimensional Multimode-Interference Optical Power Splitter

A two-dimensional multlmode-interference optical power splitter is designed and demonstrated. The new device can be used for the optical power splitting in two transverse directions. Silicon-on-lnsulator technology is utilized to fabricate the device. The performance of the device is tested.