Phononic band structure in a two-dimensional hybrid triangular graphite lattice

The propagation of acoustic wave in a two-dimensional phononic crystal of a hybrid triangular graphite array is investigated by the plane wave expansion (PWE) method. Our numerical results show that the location and width of the band gaps can be tuned by altering the radii of scatters at different positions.     

Temperature-electric field hysteresis loop of multicaloric effects in PbZr0.8Ti0.2O3 thin films

The Multicaloric effect in the PbZr_0.8Ti_0.2O₃ thin films is investigated with the application of sine wave electric field, dc electric field and stress using a phase field method combined with the thermodynamic analysis. The simulation results show that the adiabatic temperature change-electric field curve presents a shape of butterfly in the presence of the sine wave electric field. In order to detect the effect of the sine wave electric field, the multicaloric effect and the domain structures under the direct electric field and the sine wave electric field are compared. It is found that the domain switching behaviors are quite different under the different applied electric fields. And the negative multicaloric effect in the PbZr_0.8Ti_0.2O₃ thin film is attribute to the domain switching under the external field.     

铁电体中新畴成核经典模型的改进

新畴成核是外加低场下铁电体中铁电畴反转的一个重要的过程.首先介绍了新畴成核的经典模型,采用该模型研究了铁电畴反转的新畴成核过程,发现理论计算的成核速率与外场关系和实验观测结果不一致.在Tagantsev模型的基础上,选取不同的成核形状对新畴成核的经典模型进行了改进,并获得了和实验观测相符的理论计算结果. 关键词： 铁电体 铁电畴 成核速率     

多端耦合量子点分子桥的量子输运特性研究

利用非平衡格林函数方法,对五个量子点连结而成的有四个终端的耦合量子点分子桥进行了理论研究和数值模拟,得出了入射电子通过耦合量子点分子桥传输到各个终端的电子隧穿概率的规律. 关键词： 耦合量子点分子桥 非平衡格林函数 量子输运     

Gravitational Deflection of Massive Particles by a Schwarzschild Black Hole in Radiation Gauge*

The exact metric of a Schwarzschild black hole in the true radiation gauge was recently reported.In this work, we base on this gravity and calculate the gravitational deflection of relativistic massive particles up to the fourth post-Minkowskian order. It is found that the result is consistent with the previous formulations for both the case of dropping the fourth-order contribution and the case of light deflection. Our result might be helpful for future high-accuracy observations.     

Simulation study on terahertz vibrational absorption in liquid crystal compounds

The terahertz (THz) spectrum absorptions of nematic liquid crystal (LC) material, i.e. N-(p-methoxybenzylidene)-p-butylaniline (MBBA), and its relevant compounds are simulated in this paper by using the density functional theory (DFT) method. A strong absorptive frequency is located at 3.65 THz for the MBBA, which is in agreement with experimental data found in the literature. The result suggests that the DFT method is effective for dealing with the anisotropic nematic LC compounds.     

镝掺杂锆钛酸铅镧透明陶瓷的结构和电光性能

针对锆钛酸铅镧(PLZT)电光陶瓷在光调制器应用中存在工作电压偏高、场致滞后明显等不足,以镧系镝(Dy)元素对锆钛酸铅镧(Pb0.88La0.12)(Zr0.4Ti0.6)0.96O3 [PLZT(12/40/60)]线性电光材料进行掺杂改性.采用热压技术研制镝掺杂锆钛酸铅镧[Pb0.88(La1-xDyx)0.12](Zr0.40Ti0.60)0.96O3](PLDZT)(x=0.1～0.5)透明电光陶瓷.系统考察了PLDZT透明陶瓷的光学性能和电光特性及其与材料结构的相关性.研究表明,Dy掺杂导致材料晶格畸变,微量Dy掺杂有效提高了 PLZT(12/40/60)透明陶瓷的光学透过率,并且使典型的线性电光材料呈现二次电光效应特征,二次电光系数R约为5.59×10-15m2/V2;同时掺杂改性的PLDZT(x=0.1)透明陶瓷的驱动电压较未改性PLZT材料明显降低.     

Effect of fused silica subsurface defect site density on light intensification

The effect of defect density on the modulation of incident laser waves is investigated. First, based on the actual defect distribution in the subsurface of fused silica, a three-dimensional (3D) grid model of defect sites is constructed. The 3D finite-difference time-domain method is developed to solve the Maxwell equations. Then the electrical field intensity in the vicinity of the defect sites in the subsurface of fused silica is numerically calculated. The relationships between the maximal electrical field intensity in fused silica and the geometry of the defect sites are given. The simulated results reveal that the modulation becomes more remarkable with an increase of the defect density. In addition, the effect of the distribution mode of defects on modulation is discussed. Meanwhile, the underlying physical mechanism is analyzed in detail.     

Numerical analysis of birefringence and coupling length on dual-core photonics crystal fiber with complex air holes

A type of high birefringence dual-core photonic crystal fibers (DC-PCFs) with a central row of elliptical air holes have been proposed. The transverse electric field vector distributions of the two modes are evaluated, the birefringence or coupling length with the different parameters is numerically analyzed based on finite-element method. The numerical results show values for the birefringence of 8.247 × 10⁻³ (for wavelength, λ = 1.5 μm and lattice length, Λ = 1.3 μm), and for the coupling lengths about 3.1 mm and 2.6 mm (λ = 1.5 μm and Λ = 1.5 μm) to modes of x and y polarized, respectively. With the increasing of the air-filling fraction in proposed DC-PCF, the coupling length becomes longer and the birefringence becomes higher.     

Effect of defect configuration on the localization of phonons in two-dimensional phononic crystals

Effects of defect location on the defect frequency and the localization of phonons are investigated in two novel kinds of model, created by moving the location of the native cylinder and inserting an ad-cylinder in the central cellular respectively. The results show that the defect frequency in Model 1 is only related to the distance, while in Model 2, is related not only to the distance, but also to the moving direction. From the pressure distribution, obvious localization phenomenon is found. The position and shape of the localized energy are varied with the position of the defect.