Time-Dependent Variational Approach to Ground-State Phase Transition and Phonon Dispersion Relation of the Quantum Double-Well Model

The ground-state phase transition and the phonon dispersion relation of the quantum double-well model are studied by means of the time-dependent variational approach combined with a Hartree-type many-body trial wavefunction. The single-particle state is taken to be a frozen Jackiw-Kerman wavefunction. Under the condition of minimum uncertainty relation, we obtain an effective classical Hamiltonian for the system and equations of motion for the particle＇s expectation values. It is shown that the effective substrate potential transits from a symmetric double-well potential to a symmetric single-well potential, and the ground state exhibits a transition from a broken symmetry phase to a restored symmetry phase as increasing the strength of quantum fluctuations. We also obtain the phonon dispersion relations and the phonon gaps at the two phases.     

铁电单晶0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3折射率的研究

用最小偏向角法在20℃下精确测量了0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3(0.62PMN-0.38PT)单晶的折射率,给出了该温度下折射率色散的Sellmeier方程.研究了能带结构与折射率的关系,计算了样品的Sellmeier光学系数:对no,E0=5.50eV,λ0=0.226μm,S0=1.004×1014m-2,Ed=28.10eV;对ne,E0=5.57eV,λ0=0.223μm,S0=1.017×1014m-2,Ed=28.10eV.ABO3型钙钛矿材料中,BO6八面体基元决定了晶体的能带结构,对折射率产生重要影响.     

关于独立学院大学物理教学的思考

独立学院是我国高等教育在办学模式上的一种尝试,它是公办高等院校教学资源与社会资金有机结合的产物．独立学院的生源是本科第三批学生,其高考成绩一般要比本科第二批学生低几十分．其生源的特殊性,在很大程度上决定其教学方式和模式的特殊性,并直接影响着教学质量的提高．     

不同切型BaTiO3晶体二波耦合特性研究

分析了光折变晶体的电光系数对二波耦合特性的影响,二波耦合能量转移方向不仅依赖于晶体中光生载流子的电荷符号以及入射光与晶体ｃ轴的相对取向,而且依赖于晶体光系数各分量的相对大小;这种特性别明显地表现在相向二波耦合作用中。     

弛豫基铁电单晶0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3的制备与 性能研究

用改进的Bridgman法,在加入助熔剂的条件下,生长出最大尺寸为φ30×25mm^3的铌锌酸铅-钛酸铅固溶体单晶[0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3]。无宏观缺陷的晶片的典型尺寸为20×15mm^2。晶体的单晶性及其结构用X射线衍射法加以研究。所得晶体用Laue衍射法定向,取(001)晶片进行性能表征。研究了材料的介电性能,并用偏光显微镜观察了(001)晶片的电畴结构。结果表明,室温下材料的介电常数较大,为2500～5000。随着温度的升高,材料发生四方铁电相—立方顺电相的相变,相变温度为190℃左右。单晶的介电温谱呈现明显的频率色钐现象,同时,介电常数最大值的温度tm随着频率的升高而降低,观察到了电畴结构的不均匀与孪生现象。     

BaTiO3晶体自抽运相位共轭特性研究

研究了多种Rh:BaTiO3和Ce:BaTiO3晶体样品的受激背向光折变散射自抽运相位共轭特性和响应时间特性.结果表明,入射光与晶体a面或b面法线的夹角较大时,自抽运相位共轭光有更高的反射率、更快响应时间.利用前向二波耦合特性和相向二波耦合特性对实验现象给予合理的解释.实验结果表明,多数Ce:BaTiO3晶体比Rh:BaTiO3晶体的共轭光反射率高.     

阻尼作用下带对称双阱势的原子链中的洞孤子

采用多重尺度法,研究弱阻尼作用下带有对称双阱势的原子链,导出耗散型的非线性薛定谔方程,并对方程进行解析求解,给出阻尼作用下在链中传播的耗散型的洞孤子解.     

Tuning of plasmonic behaviours in coupled metallic nanotube arrays

We theoretically investigate the influence of the shape of nanoholes on plasmonic behaviours in coupled elliptical metallic nanotube arrays by the finite-difference time-domain (FDTD) method.We study the structure in two cases:one for the array aligned along the minor axis and the other for the array aligned along the major axis.It is found that the optical properties and plasmonic effects can be tuned by the effective surface charges as a result of the variation in the minor axis length.Based on the localized nature of electric field distributions,we also clearly show that the presence of localized plasmon resonant modes originates from multipolar plasmon polaritons and a large magnitude of opposing surface charges build up in the gap between adjacent nanotubes.     

Enhanced optical transmission through double-layer gold slit arrays

We investigate the relationship between the transmission and the layer distance of double-layer gold slit arrays by using the finite-difference time-domain method.The results show that the transmission properties can be influenced strongly by layer distance.We attribute the two types of resonant modes to surface plasmon resonance and the localised waveguide resonance.We find that the localised waveguide transmission peak redshifts and becomes broader with increasing layer distance D.We also describe and explain the splitting,shift,and degeneration of the surface plasmon resonant transmission peak theoretically.In addition,to clarify the physical mechanism of the transmission behaviours,we analyse the distributions of electric field and total energy for the three transmission peaks with distance D=45 nm for the double-layer system.Light transporting behaviours are mostly concentrated in the region of the slits as well as the interspaces of the two layers,and for different resonant wavelengths the electric field and energy distributions are different.It is expected that the results obtained here will be helpful for designing subwavelength metallic grating devices.