Magnetic Properties of A Cavity-Embedded Square Lattice of Quantum Dots or Antidots

Quantum electrodynamical density functional theory is applied to obtain the electronic density, spin polarization, as well as orbital and spin magnetizations of square periodic arrays of quantum dots or antidots subjected to the influence of a far-infrared cavity photon field. A gradient-based exchange-correlation functional adapted to a 2D electron gas in a transverse homogeneous magnetic field is used in the theoretical framework and calculations. The obtained results predict a non-trivial effect of the cavity field on the electron distribution in the unit cell of the superlattice, as well as on the orbital and spin magnetizations. The number of electrons per unit cell of the superlattice is shown to play a crucial role in the modification of the magnetization via the electron–photon coupling. The calculations show that cavity photons strengthen the diamagnetic effect in the quantum dot structure, while they weaken the paramagnetic effect in the antidot structure. As the number of electrons per unit cell of the lattice increases, the electron–photon interaction reduces the exchange forces that will otherwise promote strong spin splitting for both the dot and the antidot arrays.     

Decorated Ising Square Lattice in a Magnetic Field

Physics of the Solid State - The Ising model on a decorated square lattice with various parameters of exchange interactions in an external magnetic field is studied. A comparison is made with the...     

两相方腔流的格子Boltzmann模拟

利用基于Shan-Chen多相模型的格子Boltzmann方法对方腔内上板拖动的两相流动问题开展较为系统的数值模拟,详细研究雷诺数(Re),毛细数(Ca)和壁面润湿性对流动以及混合特性的影响.结果表明:Re数、Ca数越大,方腔内两相流体的混合界面长度越大,混合效果越好.另外,壁面憎水程度越高,混合界面长度增加越快,然而对于强亲水壁面,混合界面长度最终趋于一常数.     

Iterated Fully Coordinated Percolation on a Square Lattice

We study, on a square lattice, an extension to fully coordinated percolation which we call iterated fully coordinated percolation. In fully coordinated percolation, sites become occupied if all four of its nearest neighbors are also occupied. Repeating this site selection process again yields the iterated fully coordinated percolation model. Our results show a large enhancement in the size of highly connected regions after each iteration (from ordinary to fully coordinated and then to iterated fully coordinated percolation); enhancements that are much larger than an extension of correlations by an extra lattice constant might suggest. We also study the universality among the three problems by determining the corresponding static and dynamic critical exponents. Specifically, a new method to directly calculate the walk dimension, d _w , using finite size scaling applied to normal mode analysis is used. This method is applicable to any geometry and requires significantly less computation than previously known calculations to determine d _w .     

Kawasaki Dynamics on Square Lattice

The bond-moving and decimation renormalization group techniques are applied to obtaining the critical dynamic exponent of the Kawasaki-king model on square lattice. The result is found to be z = z_g + 2, where z_g, is the critical dynamic exponent of the Glauber model on the same lattice. We guess that the relation may be valid for all d-dimensional systems with d≥2.     

Modulation of Magneto-Intersubband Oscillations in a One-Dimensional Lateral Superlattice

JETP Letters - Low-temperature magnetotransport in a quasi-two-dimensional electron system based on a selectively doped GaAs quantum well with two occupied quantum-confinement subbands with...     

Berezinskii-Kosterlitz-Thouless Transition in a Two-Dimensional Random-Bond XY Model on a Square Lattice

We perform Monte Carlo simulations to study the two dimensional random-bond XY model on a square lattice. Two kinds of bond randomness with the coupling coefficient obeying the Gaussian or uniform distribution are discussed. It is shown that the two kinds of disorders lead to similar thermodynamic behaviors if their variances take the same value. This result implies that the variance can be chosen as a characteristic parameter to evaluate the strength of the randomness. In addition, the Berezinskii-Kosterlitz-Thouless transition temperature decreases as the variance increases and the transition can even be destroyed as long as the disorder is strong enough.     

Lattice Green's Function for Infinite Square Lattice in the Second Nearest-Neighbour Interaction Approximation

In dealing with the square lattice model,we replace the traditionally needed Born-Von Karmann periodic boundary condition with additional Hamiltonian terms to make up a ring lattice.In doing so,the lattice Green's function of an infinite square lattice in the second nearest-neighbour interaction approximation can be derived by means of the matrix Green's function method.It is shown that the density of states may change when the second nearest-neighbour interaction is turned on.     

二维正方晶格Compass-XY模型的方向序和拓扑序

采用Monte Carlo方法研究二维正方晶格Compass-XY模型,通过调节过渡参量α,计算了降低交换相互作用的阻挫对方向序和拓扑序的影响.结果表明,方向序和拓扑序之间的转变是一个逐渐过渡的过程,并不存在明显的界限.在某一范围内,这两种序是相互重叠的,难以区分.阻挫的降低,易于形成拓扑序,同时会抑制方向序.当阻挫变得足够弱时,方向序被破坏.     

Coexistence and Extinction Pattern of Asymmetric Cyclic Game Species in a Square Lattice

The co-evolutionary dynamics of a cyclic game system is investigated in a two-dimensional square lattice with the asymmetrical rates for three species. Different with the well-mixed system, coexistence and extinction emerge alternately in the system, where a ＂zero-one＂ behavior is robust for a small population size, whereas, the system is predominated by coexistence for a big population one. We study in detail the influence about the fluctuation to the change of the state, and find that the difference between the maximal amplitude about the fluctuation and the average intensity determines which state the system is ultimately. In addition, we introduce Ports energy to explain the reason of the ＂zero-one＂ behavior. It is shown that the average Ports energy per site is the distance to the ＂zero-one＂ behavior in the model.     

Area Distribution of Two-Dimensional Random Walks on a Square Lattice

The algebraic area probability distribution of closed planar random walks of length N on a square lattice is considered. The generating function for the distribution satisfies a recurrence relation in which the combinatorics is encoded. A particular case generalizes the q-binomial theorem to the case of three addends. The distribution fits the Lévy probability distribution for Brownian curves with its first-order 1/N correction quite well, even for N rather small.     

Features of Magneto-Intersubband Oscillations in HgTe Quantum Wells

JETP Letters - Magneto-intersubband oscillations (MISOs) in single quantum wells of the gapless semiconductor HgTe have been studied experimentally. It has been shown that, in contrast to MISOs in...     

Decomposition of the Fock Space in Two-Dimensional Square Lattice Systems

We discuss how to decompose the Fock space of a many-fermion system embedded in two-dimensional square lattice. Wefirst notice that the symmetry group inherent in the system is one of the two-dimensional space groups. We shortly review thecorresponding irreducible representations of the group. We then find the characters of the reducible representation of the many-fermion Fock space. Using the characters, we obtain the multiplicity of each irreducible representation contained in the Fock space of a fixed number of fermions. We present specific examples, where we calculate the multiplicities which are the dimensions of the decomposed spaces.     

Thermal Lattice Boltzmann Flux Solver for Natural Convection of Nanofluid in a Square Enclosure

In the present study, mathematical modeling was performed to simulate natural convection of a nanofluid in a square enclosure using the thermal lattice Boltzmann flux solver (TLBFS). Firstly, natural convection in a square enclosure, filled with pure fluid (air and water), was investigated to validate the accuracy and performance of the method. Then, influences of the Rayleigh number, of nanoparticle volume fraction on streamlines, isotherms and average Nusselt number were studied. The numerical results illustrated that heat transfer was enhanced with the augmentation of Rayleigh number and nanoparticle volume fraction. There was a linear relationship between the average Nusselt number and solid volume fraction. and there was an exponential relationship between the average Nusselt number and Ra. In view of the Cartesian grid used by the immersed boundary method and lattice model, the immersed boundary method was chosen to treat the no-slip boundary condition of the flow field, and the Dirichlet boundary condition of the temperature field, to facilitate natural convection around a bluff body in a square enclosure. The presented numerical algorithm and code implementation were validated by means of numerical examples of natural convection between a concentric circular cylinder and a square enclosure at different aspect ratios. Numerical simulations were conducted for natural convection around a cylinder and square in an enclosure. The results illustrated that nanoparticles enhance heat transfer in higher Rayleigh number, and the heat transfer of the inner cylinder is stronger than that of the square at the same perimeter.     

Quantum Phase Transition on a Spin-One Spatially Anisotropic Frustrated Zigzag Square Lattice

We study quantum phase transitions in the easy-plane spin-one Heisenberg model on a zigzag square lattice with next-nearest-neighbor interactions at zero temperature using the SU(3) Schwinger boson formalism in a mean field approximation. We present the phase diagram and the dispersion relation for several values of the parameters. A magnetically disordered region in the phase diagram is found, even when the anisotropy parameter vanishes.     

Critical Ising on the Square Lattice Mixes in Polynomial Time

The Ising model is widely regarded as the most studied model of spin-systems in statistical physics. The focus of this paper is its dynamic (stochastic) version, the Glauber dynamics, introduced in 1963 and by now the most popular means of sampling the Ising measure. Intensive study throughout the last three decades has yielded a rigorous understanding of the spectral-gap of the dynamics on everywhere except at criticality. While the critical behavior of the Ising model has long been the focus for physicists, mathematicians have only recently developed an understanding of its critical geometry with the advent of SLE, CLE and new tools to study conformally invariant systems.     

Lattice Dynamics and Inelastic Nuclear Resonant X-Ray Scattering

Measurement of thermal and elastic properties of materials, like phonon density of states, specific heat or speed of sound, by a new X-ray scattering technique is presented. Inelastic nuclear resonant scattering of X-rays produced from new electron storage rings, coupled with advances in high-energy-resolution crystal optics and fast detectors has enabled the development of a new method of analyzing the energy loss in a scattering process with a resolution of 10⁷ or better in the X-ray region of 6–30 keV. Some unique aspects like element (isotope) selectivity, the amount of material needed for analysis (nanograms) and physical size that X-rays can be focused (5 micrometer or better) favors this approach over more established techniques of neutron scattering, Mössbauer, and Raman spectroscopy. Applications to several unique cases (e.g., multilayers and high pressure) are discussed.     

Unusual Corrections to Scaling in the 3-State Potts Antiferromagnet on a Square Lattice

At zero temperature, the 3-state antiferromagnetic Potts model on a square lattice maps exactly onto a point of the 6-vertex model whose long-distance behavior is equivalent to that of a free scalar boson. We point out that at nonzero temperature there are two distinct types of excitation: vortices, which are relevant with renormalization-group eigenvalue 1/2 and non-vortex unsatisfied bonds, which are strictly marginal and serve only to renormalize the stiffness coefficient of the underlying free boson. Together these excitations lead to an unusual form for the corrections to scaling: for example, the correlation length diverges as J/kT according to Ae ² (1+be ^– +···), where b is a nonuniversal constant that may nevertheless be determined independently. A similar result holds for the staggered susceptibility. These results are shown to be consistent with the anomalous behavior found in the Monte Carlo simulations of Ferreira and Sokal.     

Scattering effect of atoms through a Bose-Einstein condensate in an optical Lattice with a single defect

We study the transport of atoms across a localized Bose-Einstein condensate in an onedimensional optical lattice with a single defect. Our analytical and numerical results show that the defect as well as the nonlinear parameter can control the transmission of the atoms beam and the position of total reflection caused by Fano resonance. These interesting features may be a very useful basis for devising tunable atom filters or a button.