抛物量子线中强耦合极化子的有效质量

采用改进的线性组合算符法、Lagrange乘子和变分法,在考虑电子与LO声子相互作用情况下,研究了抛物量子线中强耦合极化子的有效质量和光学声子平均数。通过数值计算,讨论了约束强度ω₀和拉格朗日乘子u对极化子的有效质量m^*和光学声子平均数N及极化子振动频率λ的影响。计算结果表明:有效质量m^*和光学声子平均数N及极化子振动频率λ都随着约束强度ω₀和拉格朗日乘子u的增加而增大。     

一维铁磁/有机共轭聚合物的自旋极化研究

针对最近关于自旋注入有机体的实验研究，理论上计算了有机分子与磁性原子接触时的自旋极化现象.通过调节磁性原子的自旋劈裂强度，发现有机分子链内的自旋极化弱于金属链，但强于半导体链.同时还研究了有机分子链内自旋极化随电子-声子耦合强度的变化关系以及界面耦合的自旋相关效应. 关键词： 界面耦合 自旋极化 自旋劈裂     

耦合广义非线性薛定谔方程的相互作用表象龙格库塔算法及其误差分析

本文通过表象变换, 将耦合广义非线性薛定谔方程 (C-GNLSE) 变换成相互作用表象中的向量方程, 再利用向量形式的4阶龙格-库塔迭代格式, 建立了一种在频域内求解C-GNLSE的同步更新迭代算法. 通过将该向量形式的相互作用表象中的4阶龙格-库塔 (V-JH-RK4IP) 算法应用于高双折射光子晶体光纤中超连续谱产生的数值模拟, 验证了算法的有效性, 通过与现有其他典型算法的比较, 表明以V-JH-RK4IP算法求解C-GNLSE具有最高的计算精度和计算效率. 关键词： 耦合广义非线性薛定谔方程(C-GNLSE) 相互作用表象 4阶龙格-库塔算法 超连续谱产生     

有机自旋器件磁性渗透层中双极化子对自旋极化输运的影响

根据实验发现的有机器件如Co/有机半导体/La_0.7Sr_0.3MnO₃中磁性原子渗透现象, 利用自旋漂移-扩散方程, 理论研究了磁性渗透层中极化子-双极化子的转化对自旋极化输运的影响. 研究发现: 磁性渗透层具有不同于纯净有机层的迁移率和自旋反转时间, 都将影响极化子-双极化子的转化, 进而影响自旋极化的输运; 在磁性渗透层中极化子自旋反转时间的劈裂是引起自旋弛豫的主要因素, 而极化子和双极化子之间的转化是重要因素.     

一维分子晶体系统的极化子-孤子压缩态、系统基态性质和量子涨落

基于一维分子晶体系统的 Holstein 模型,采用压缩-相干态展开方法,计及电子-声子间量子关联和重整化平移修正,分析和研究电子-双声子相互作用对极化子-孤子系统基态性质和量子涨落的影响.推导了一维极化子-孤子系统的封闭形式非线性方程.应用非线性项展开方法,给出非线性方程的解析解和相关基态特性结果.研究表明,仅当电子-双声子耦合强度 g₁<0时非线性方程才有孤波解,此时声子量子涨落效应随着压缩的增加,极化子-孤子系统基态能量变得更负,孤子局域减少,孤子态更加稳定;另一方面,电子密度涨落〈Δ²n〉和声子坐标-动量的不确定量〈Δ²p〉〈Δ²q〉比无声子压缩效应的大,极化子结合能变得更负.特别是,当g₁<0时,双声子效应的量子涨落〈Δ²n〉与〈Δ²p〉〈Δ²q〉的值比单声子情况有明显增加. 关键词： 压缩-相干态展开 极化子-孤子态与量子涨落 电子-双声子相互作用 非线性薛定谔方程     

强子结构函数的数值解法

为了避免矩方法求解强子结构函数时对函数待定形式的依赖并提高解的精确度,本文采用把A-P方程离散为常微分方程组,用龙格-库塔方法求解的方法,得出随Q²变化的价夸克、海夸克和胶子的结构函数。     

He-Na2体系低温下的冷碰撞研究

在已经拟合好的He-Na₂体系势能面上,根据原子-双原子分子的非反应性碰撞动力学的相关基本理论,在空间固定坐标系下,采用严格的密耦方法求解了He原子和Na₂分子的转动非弹性碰撞动力学方程.并对He-Na₂体系的微分散射截面、积分截面作了详细的分析,结果与实验符合得比较好.结果表明：（1）弹性散射（Δj=0）截面远大于非弹性截面;（2）较小Δj的跃迁主要产生前向散射,随着Δj的增加,后向散射的几率增加 关键词： 2体系')" href="#">He-Na₂体系 密耦方法 微分散射截面 积分截面     

自旋为1的三粒子Heisenberg XXX链中杂质对热纠缠的影响

采用纠缠的度量方法Negativity研究了匀强磁场下自旋为1的含杂质三粒子Heisenberg XXX链的热纠缠特性.通过计算系统的杂质位与其余部分间的两体纠缠N_1-23及正常位与其余部分间的两体纠缠N_12-3,发现纠缠存在的临界温度T_c的改变来自杂质参数J₁的变化,随杂质参数J₁的增加而增加,外界磁场B< 关键词： 热纠缠 XXX链')" href="#">Heisenberg XXX链 杂质     

高次正幂与逆幂势函数的叠加的径向薛定谔方程的解析解

当薛定谔方程中出现高次非谐振子势，电偶极矩势，分子晶体势，极化等效势等高次正幂与逆幂势函数以及它们的叠加时，薛定谔方程的求解变得非常复杂，采用奇点邻域附近的级数解法与求解渐近解相结合，在多种相互作用幂函数紧密耦合的条件下，得到势函数为V(r)=a₁r⁶+a₂r²+a₃r^{-4关键词： 级数解法 幂势函数 径向波函数 渐近解}     

采用多参考组态相互作用方法研究AsN( X1 Σ+ )自由基的光谱常数与分子常数

采用内收缩多参考组态相互作用方法和相关一致基对AsN(X ¹ Σ⁺)自由基的势能曲线进行了研究. 计算过程中对两原子分别采用不同基组,As原子为aug-cc-pV5Z基组,N原子为aug-cc-pV6Z基组. 通过最小二乘法将势能曲线拟合成Murrell-Sorbie函数,并进一步计算得到AsN(X ¹ Σ⁺)自由基的光谱常数.光谱常数分别为D_e=4.97 eV,R_e=0.16259 nm, ω_e=1061.14 cm^-1, ω_ex_e=5.4715 cm^-1, B_e=0.53919 cm^-1和α_e=0.003409 cm^-1. 通过比较发现它们与实验值符合非常好. 利用得到的解析势能函数, 求解双原子分子核运动的径向Schrödinger方程, 找到了J=0时该自由基存在的全部67个振动态. 对于每一振动态, 分别计算了振动能级、经典转折点、惯性转动常数和离心畸变常数. 与实验结果比较后发现,计算结果达到了很高的计算精度. 关键词： AsN 势能曲线 光谱常数 分子常数     

A simulation study on p-doping level of polymer host material in P3HT:PCBM bulk heterojunction solar cells

In this study,we investigate the influence of doping on the charge transfer and device characteristics parameters in the bulk heterojunction solar cells based on poly(3-hexylthiophene)(P3HT) and a methanofuUerene derivative(PCBM).Organic semiconductors are also known to be not pure and they have defects and impurities,some of them are being charged and act as p-type or n-type dopants.Calculations of the solar cell characteristics parameters versus the p-doping level have been done at three different n-dopings(N_d) that consist of 5 × 10~(17) cm~(-3),10~(18) cm~(-3),and 5 × 10~(18) cm~(-3).We perform the analysis of the doping concentration through the drift-diffusion model,and calculate the current and voltage doping dependency.We find that at three different n-dopant levels,optimum p-type doping is about N_p = 6 × 10~(18) cm~(-3).Simulation results have shown that by increasing doping level,V_(oc) monotonically increases by doping.Cell efficiency reaches its maximum at somewhat higher doping as FF has its peak at N_p = 3 × 10~(18) cm~(-3).Moreover,this paper demonstrates that the optimum value for the p-doping is about N_p = 6 × 10~(18) cm~(-3) and optimum value for n-dopant is N_d = 10~(18) cm~(-3),respectively.The simulated results confirm that doping considerably affects the performance of organic solar cells.     

N-cluster correlations in four- and five-dimensional percolation

We study N-cluster correlation functions in four- and five-dimensional (4D and 5D) bond percolation by extensive Monte Carlo simulation. We reformulate the transfer Monte Carlo algorithm for percolation [Phys. Rev. E72, 016126 (2005)] using the disjoint-set data structure, and simulate a cylindrical geometry L^d−1 × ∞, with the linear size up to L = 512 for 4D and 128 for 5D. We determine with a high precision all possible N-cluster exponents, for N =2 and 3, and the universal amplitude for a logarithmic correlation function. From the symmetric correlator with N=2, we obtain the correlationlength critical exponent as 1/ν=1.4610(12) for 4D and 1/ν=1.737(2) for 5D, significantly improving over the existing results. Estimates for the other exponents and the universal logarithmic amplitude have not been reported before to our knowledge. Our work demonstrates the validity of logarithmic conformal field theory and adds to the growing knowledge for high-dimensional percolation.     

三角翼大迎角非对称旋涡破裂数值模拟

采用由伪时间子迭代格式实现的二阶精度LU SGS方法进行时间推进,并以Jameson中心加人工粘性格式进行空间离散,应用层流假设和Baldwin Lomax(B-L)模式,求解雷诺平均的薄层Navier Stokes(N-S)方程组以模拟细长三角翼大迎角流动.为验证本方法,首先计算了具备实验数据的65°后掠角三角翼大迎角流场,获得令人满意的结果;然后模拟了80°后掠角的细长三角翼,研究其大迎角非对称旋涡破裂特性.     

Branes, geometry and N = 1 duality with product gauge groups of SO and Sp

We study N = 1 dualities in four-dimensional supersymmetric gauge theories as the world volume theory of D4 branes with one compact direction in type IIA string theory. We generalize the previous work for SO(N_c1) × Sp(N_c2) with the superpotential W = TrX⁴ to the case of W = TrX^4(k+1) in terms of brane configuration. We conjecture that the new dualities for the product gauge groups of SO(N_c1) × Sp(N_c2) × SO(N_c3), SO(N_c1) × Sp(N_c2) × SO(N_c3) × Sp(N_c4) and higher multiple product gauge groups can be obtained by reversing the ordering of NS5 branes and D6 branes while preserving the linking numbers. We also describe the above dualities in terms of wrapping D6 branes around 3-cycles of Calabi-Yau threefolds in type IIA string theory. The theory with adjoint matter can be regarded as taking multiple copies of NS5 brane in the configuration of brane or geometric approaches.     

Simulations of the effects of density and temperature profile on SMBI penetration depth based on the HL-2A tokamak configuration

Using the trans-neut module of the BOUT++ code, we study how the fueling penetration depth of supersonic molecular beam injection(SMBI) is affected by plasma density and temperature profiles. The plasma densities and temperatures in L-mode are initialized to be a set of linear profiles with different core plasma densities and temperatures. The plasma profiles are relaxed to a set of steady states with different core plasma densities or temperatures. For a fixed gradient, the steady profiles are characterized by the core plasma density and temperature. The SMBI is investigated based on the final steady profiles with different core plasma densities or temperatures. The simulated results suggest that the SMB injection will be blocked by dense core plasma and high-temperature plasma. Once the core plasma density is set to be N_(i0)= 1.4N_0(N_0= 1 × 10~(19)m~(-3)) it produces a deeper penetration depth. When N_(i0) is increased from 1.4N_0 to 3.9N_0 at intervals of 0.8N_0, keeping a constant core temperature of T_(e0)= 725 eV at the radial position of ψ = 0.65, the penetration depth gradually decreases. Meanwhile, when the density is fixed at N_(i0)= 1.4N_0 and the core plasma temperature T_(e0) is set to 365 eV,the penetration depth increases. The penetration depth decreases as T_(e0) is increased from 365 eV to 2759 eV. Sufficiently large N_(i0) or T_(e0) causes most of the injected molecules to stay in the scrape-off-layer(SOL) region, lowering the fueling efficiency.     

氢化非晶硅薄膜晶体管的低频噪声特性

针对氢化非晶硅薄膜晶体管(hydrogenated amorphous silicon thin film transistor,a-Si:H TFT)的低频噪声特性展开实验研究.由测量结果可知,a-Si:H TFT的低频噪声特性遵循1/f~γ(f为频率,γ≈0.92)的变化规律,主要受迁移率随机涨落效应的影响.基于与迁移率涨落相关的载流子数随机涨落模型(?N-?μ模型),在考虑源漏接触电阻、局域态俘获及释放载流子效应等情况时,对器件低频噪声特性随沟道电流的变化进行分析与拟合.基于a-Si:H TFT的亚阈区电流-电压特性提取器件表面能带弯曲量与栅源电压之间的关系,通过沟道电流噪声功率谱密度提取a-Si:H TFT有源层内局域态密度及其分布.实验结果表明:局域态在禁带内随能量呈e指数变化,两种缺陷态在导带底密度分别约为6.31×10~(18)和1.26×10~(18)cm~(-3)·eV~(-1),特征温度分别约为192和290 K,这符合非晶硅层内带尾态密度及其分布特征.最后提取器件的平均Hooge因子,为评价非晶硅材料及其稳定性提供参考.     

Conditional observability

For a quantum Hamiltonian H=H(λ), the observability of the energies E may be robust (whenever all E are real at all λ) or, otherwise, conditional. Using a pseudo-Hermitian family of N-state chain models H=H^(N)(λ) we discuss some generic properties of conditionally observable spectra.     

激光照射中Z薄靶等离子体状态的计算-激光等离子体相互作用的理论模拟(Ⅰ)

本文叙述用一维非平衡辐射流体力学激光打靶程序模拟计算高功率密度(~10¹³W/cm²)激光照射中Z介质薄靶形成的等离子体状态。考虑的物理过程有轫致、光电离、电子碰撞电离及它们的逆过程,Compton散射过程等。Compton散射采用Fokker-Planck近似;电子和离子热传导采用限流扩散近拟;光子方程采用多群限流扩散近似;用平均原子模型计算布居数。激光的吸收主要考虑逆轫致吸收。用功率密度分别为5×10¹³W/cm²和1×10¹⁴W/cm²,波长0.53μm,脉宽450ps的激光从两面和单面打se薄靶,模拟计算结果与国外的实验结果^[1]一致。     

Does the quenched reduced U(∞) chiral model break spontaneously in weak coupling?

The U(N) chiral model, when quenched using Parisi's rule, has a [U(1) × U(1)]^N/U(1) global invariance. To determine whether this symmetry breaks spontaneously in weak coupling for N=∞, a one-loop calculation of the distribution of eigenvalues of the single U(N) matrix of the model is performed. This distribution is shown to be uniform on the unit circle and hence, no symmetry breaking occurs. Further, the order parameter | tr U|²/N², which should be zero at N=∞ in the absence of spontaneous symmetry breaking, is evaluated in the weak coupling phase for one, two and three dimensions for N varying from 2 to 50 by Monte Carlo simulation of the quenched model. The data indicate that this parameter indeed goes to zero as N→∞ implying that the symmetry does not break.     

N=2 6-dimensional supersymmetric E6 breaking

We study the N=2 supersymmetric E₆ models on the 6-dimensional space–time where the supersymmetry and gauge symmetry can be broken by the discrete symmetry. On the space–time M⁴×S¹/(Z₂×Z₂′)×S¹/(Z₂×Z₂′), for the zero modes, we obtain the 4-dimensional N=1 supersymmetric models with gauge groups SU(3)×SU(2)×SU(2)×U(1)², SU(4)×SU(2)×SU(2)×U(1), and SU(3)×SU(2)×U(1)³ with one extra pair of Higgs doublets from the vector multiplet. In addition, considering that the extra space manifold is the annulus A² and disc D², we list all the constraints on constructing the 4-dimensional N=1 supersymmetric SU(3)×SU(2)×U(1)³ models for the zero modes, and give the simplest model with Z₉ symmetry. We also comment on the extra gauge symmetry breaking and its generalization.