磁场中量子点四电子系统的基态性质

利用少体物理的方法，研究了磁场中二维量子点四电子系统基态能量与角动量间的变化关系，以及磁场强度和约束势的大小对四电子系统基态的影响.数值计算表明，量子力学对称性是幻数角动量出现的重要因素. 关键词：     

介质阻挡放电斑图中放电通道的相互作用研究

在近大气压介质阻挡放电中，研究了六边形斑图的空间波长随放电参数的变化，仔细观察了稳定的六边形中放电通道的产生及运动行为.结果表明空间波长随电压增加而减小，变化曲线与放电间隙和气压有关.电压升高，边界处生成新的放电丝，位于六边形最外层顶点处新生成的放电丝沿径向运动，而位于六边形边长上新生成的放电丝的运动方向平行于距其最近的C₂轴(过六边形顶点). 继续升高电压，放电丝变为条状进而形成螺旋波或靶波.在观察实验结果和分析放电丝受力的基础上，认为放电区域可能存在一种类似二维库仑晶体中存在的约束势. 关键词： 介质阻挡放电 斑图 放电通道 约束势     

具有在位势的一维双原子链晶格振动的色散关系

在简谐近似下,求解具有在位势的一维双原子链晶格振动运动方程,得到了具有在位势的晶格振动的色散关系.在位势使色散关系声频支在布里渊区中心的振动频率不再为零,并且随在位势的增大而增大.对于原子之间相互作用势不随在位势大小变化的情况下,晶格振动的色散关系的频隙随在位势的增大而变宽.讨论了原子链由只有在位势的不连续极限(AC极限),通过在位势逐渐减弱而原子间相互作用势逐渐增强,最后演变到只有原子间相互作用势的原子链的情况.随着在位势减弱和相互作用势增强,色散关系的频隙由AC极限的孤立轻、重原子简谐振动频率之差逐渐变化到通常的无在位势的色散关系频隙.     

大气压氦气介质阻挡放电单-多柱演化动力学

介质阻挡放电被众多工业领域用作低温等离子体源,柱状放电是介质阻挡放电的重要形式之一,但其放电理论尚未掌握.进行大气压氦气介质阻挡放电实验,通过降低外施电压低于起始放电电压实现了柱状放电从单柱到多柱的斑图演化,拍摄了电极底面放电图像,测量了外施电压、放电电流、放电转移电荷、放电柱的柱直径和柱间距,计算了放电柱受其他所有柱施加的库仑力与磁场力.结果表明:外施电压变化瞬间电极底面放电图像呈现出动态演化过程.不同层放电柱的柱直径由中心向外层依次增大.计算发现演化稳定后放电柱所受库仑力远大于磁场力,推理存在一约束势平衡库仑力使放电柱稳定分布.不同电压、位置的放电柱所受库仑力不同:不同层的放电柱所受库仑力由最外层至中心柱依次减小,中心柱受力为0,最外层放电柱的约束势应最大而中心放电柱的约束势应该最小;外施电压降低,介质表面电荷和放电柱总数的共同作用导致库仑力增大,约束势也应有所增大,即约束势受介质表面电荷、放电柱总数与位置的共同影响.     

具有在位势的一维双原子链晶格振动的长声学波图像

通过数值求解具有在位势的一维双原子链晶格振动的运动方程组,给出了具有不同大小在位势的长声学波振动模图像,直观展示出在位势使原胞中两种原子的振动位移不同,并且随在位势的增大,振动位移之差显著增大.     

弱磁场中弱相互作用费米气体的热力学性质

根据赝势法和系综理论导出弱磁场中弱相互作用费米气体的内能、化学势和热容量的小参数r的解析式.在此基础上给出高温和低温两种情况下弱磁场中弱相互作用费米气体的热力学性质,探讨磁场及粒子间相互作用对热力学性质的影响,分析磁场与三维谐振势两种约束对系统性质影响的不同及其原因. 关键词： 赝势法 费米气体 相互作用 热力学性质     

相对论微观光学势的自洽计算

本文以Walecka模型及非线性σ模型自洽计算了¹⁶O、⁴⁰Ca的相对论微观光学势.得到的标量势和矢量势符号相反,大小约为几百MeV,与核子的质量可以相比拟.为了与非相对论光学势比较,给出了Schrodinger等价势.这个等价势在很大的能量范围(E=200MeV以下)内适用,相对论计算自然地得到较强的能量相关的自旋-轨道耦合势,与唯象分析一致.本文用洽计算的实部势及最低级的虚部势计算了核子-核散射微分截面及极化率,得到与实验较好的符合.非线性σ模型给出合理的核的不可压缩系数,从而考虑了核的表面效应,改善了计算的光学势.     

铝中空位形成能计算时的原胞尺寸等参数效应

使用第一原理赝势法计算简单金属铝中空位的形成能，详细讨论空位形成能的理论计算值与所用超原胞大小、k点数等参数的关系.结果显示，使用第一原理的超原胞方法计算单个空位的形成能时，超原胞的大小应取到百余个原子.用108个原子的超原胞进行计算时，所得结果与实验值符合很好. 关键词：     

电磁AB效应与描述电磁场的基本物理量

本文通过介质电磁AB效应及其实验验证，论述了描述电磁场的基本物理量应为规范条件约束下的电磁势（φ，A），而不是场量（E，B）。     

理想气体中的内势能

本文证明在无壁空间或无束缚力约束空间中,压力是气体以物态存在的束缚力.证明了热力学压力不仅是动量交换的统计平均值的量度,而且也是分子或原子空间位置分布(密度)的表征.理想气体在有限空间中的统计构形空间,具有逸散势-pV.这种系统构形空间内的各能级粒子具有相应的动量空间分布,其统计构形空间具有无序势TS.热力学平衡态具有处处相等p、T和总势能TS-pV.理想气体的二种势能具有对称性,总势能等于零;但其相应的无序势和逸散势都不等于零.     

Parameter-tunable doublet–quadruplet transition in a three-electron quantum dot

A three-electron quantum dot under an external magnetic field was studied. A number of phase diagrams have been obtained to demonstrate how the variation of the magnetic field and/or the parameters of confinement would lead to the occurrence of doublet–quadruplet transitions. Both the confinement with parabolic potential and the square well potential have been considered. We show that the parameters of confinement alter the ground state of the quantum dot from a spin doublet to a spin quadruplet. This result indicates that the quantum dot can be used as a good candidate for qubit of a quantum computer.     

Optical transitions in parabolic quantum dot

Direct optical absorption of light is theoretically investigated in a spherical quantum dot from GaAs. The confinement potential of the dot is approximated as parabolic. Three regimes of size quantization are discussed: weak, strong, and intermediate. The corresponding threshold frequencies of absorption are determined. A comparison with the case of a spherical quantum dot with rectangular infinitely high confinement potential is performed.     

Stark Splitting of the Energy Spectrum in a Two-Electron Quantum Dot

A two-electron quantum dot model assuming the existence of the image charge is formulated in the present paper. Based on this model, the effective electron confinement potential is calculated by the self-consistent method. It is established that the electron confinement potential in the quantum dot has both symmetric and antisymmetric parts. An analysis of this potential demonstrates that the tunnel electron transition in the quantum dot can occur only in the direction perpendicular to the film plane. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 9–20, May, 2005.     

Tailoring magnetism in quantum dots

We study magnetism in magnetically doped quantum dots as a function of the confining potential, particle numbers, temperature, and strength of the Coulomb interactions. We explore the possibility of tailoring magnetism by controlling the nonparabolicity of the confinement potential and the electron-electron Coulomb interaction, without changing the number of particles. The interplay of strong Coulomb interactions and quantum confinement leads to enhanced inhomogeneous magnetization which persists at higher temperatures than in the noninteracting case. The temperature of the onset of magnetization can be controlled by changing the number of particles as well as by modifying the quantum confinement and the strength of the Coulomb interactions. We predict a series of electronic spin transitions which arise from the competition between the many-body gap and magnetic thermal fluctuations.     

Dispersion Theory of Polaron in a Parabolic Quantum Dot at Finite Temperatures

By using the dispersion theory instead of the Fröhlich Hamiltonian, the polaron energy in a quantum dot with a parabolic confinement potential is investigated at finite temperatures. It is found that the self-trapping energy of the polaron decreases with the increasing temperature, and the temperature effect is more obvious in quantum dots with weaker confinement.     

库仑场对量子线中强耦合极化子性质的影响

采用改进的线性组合算符法研究了库仑场对抛物量子线中强耦合极化子性质的影响。计算了抛物量子线中强耦合束缚极化子的基态能量、振动频率和声子平均数。讨论了这些量对库仑束缚势和约束强度的依赖关系。数值计算结果表明：量子线中强耦合束缚极化子的基态能量随库仑束缚势的增加而减少,随约束强度的增加而增大;振动频率和电子周围的光学声子平均数均随库仑束缚势的增加而增加。     

库仑场对抛物量子点中强耦合极化子性质的影响

采用线性组合算符和幺正变换方法研究了在库仑场束缚下抛物量子点中强耦合束缚极化子的振动频率和基态能量。并对其进行了数值计算,结果表明:强耦合束缚极化子的振动频率和基态能量随量子点的有效受限长度的增加而减小,随电子-LO声子耦合强度的增加而增加,束缚极化子的基态能量随库仑势的增加而减小。     

Optical absorptions of an exciton in a quantum ring: Effect of the repulsive core

We study the optical absorptions of an exciton in a quantum ring. The quantum ring is described as a circular quantum dot with a repulsive core. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The linear, third-order nonlinear and total optical absorption coefficients have been examined with the change of the confinement potential. The results show that the optical absorptions are strongly affected by the repulsive core. Moreover, the repulsive core can influence the oscillation in the resonant peak of the absorption coefficients.     

Modeling of confinement potential for cylindrical quantum dot

Quantum states and energy levels of an electron in a cylindrical quantum dot with different models of confinement potentials are studied. Two models of confinement potentials, Morse potential and modified Pöschl-Teller potential, are considered. It is shown that due to distinction between symmetric and asymmetric nature of potentials, there is a fundamental difference in behavior of the ground levels of charge carriers in these potentials. At small values of the width of Morse potential, quantum emission of electron occurs which is not observed in case of the modified Pöschl-Teller potential.     

纳米材料SnO2表面声子模的红外光谱研究

利用红外光谱法研究了球形SnO₂纳米微粒的表面声子模特性,在实验上观察到了全部Frohlich模,并与理论计算结果进行了比较,讨论了空间量子限域效应对SnO₂纳米微粒红外光谱特性的影响。 关键词：