电子磁矩对同步辐射频谱的修正

本文从偶极子辐射场的Heaviside-Feynman表达式出发, 用经典的电动力学方法推导了考虑内禀磁矩影响后的相对论电子辐射频谱分布的表达式, 并对做匀速圆周运动的极端相对论性电子的同步辐射, 计算了两个偏振方向上的考虑磁矩修正后的辐射谱. 计算结果表明对于特征频率为ω_c的同步辐射, 如果ħω_c≥10 keV, 内禀磁矩对辐射的修正是可观的. 通过同步辐射的内禀磁矩修正, 本文讨论了电子束极化度与辐射场偏振度的依赖关系, 并基于此关系提出一种测量电子束极化度的新方法. 关键词： 同步辐射 电子内禀磁矩 同步辐射偏振度 束流极化度     

从Sn质子滴线核到Sn中子滴线核的自旋对称性和赝自旋对称性

在球形相对论平均场模型下, 采用NLSH相互作用全面研究了从Sn质子滴线核到Sn中子滴线核的自旋对称性和赝自旋对称性. 发现: 1) 随着核子数的增大, 中子和质子的赝自旋波函数劈裂基本上都是减小的, 并且质子的变化趋势更加明显. 中子高能级的自旋波函数劈裂随着核子数的增大也是减小的. 2) 对于特定的同位素, 当n=1时, 赝自旋波函数劈裂随着l的增大而增大. 当n=2时, 中子的自旋波函数劈裂随着l的增大而增大. 当l=2或l=3时, 中子的自旋波函数劈裂随着n的增大而增大. 3) 中子和质子的赝自旋劈裂之间的差别总是比自旋劈裂的差别更大一些.     

铁磁/有机半导体/铁磁系统的电流自旋极化性质研究

根据有机半导体中的电流自旋极化注入和输运实验现象，理论上研究了铁磁/有机半导体/铁磁系统的电流自旋极化性质.考虑到有机半导体的具体特性，从自旋扩散理论和欧姆定律出发，得到了系统的电流自旋极化率.假设自旋极化子和不带自旋的双极化子为有机半导体中的载流子.通过计算发现，极化子为实现有机半导体中电流极化注入和输运的有效自旋载流子，即使它只占总载流子很少一部分.还进一步研究了自旋相关界面电阻和电导率匹配以及有机半导体长度等因素对系统电流自旋极化的影响. 关键词： 自旋电子学 自旋注入 有机半导体 极化子     

Spin Correlations in Top Quark Pair Production Near Threshold at the e^＋e^- Linear Collider

We investigate the spin correlations in top quark pair production near the threshold at the e^ e^- linear collider. Comparing with the results above the threshold region, we find that near the threshold region the off-diagonal basis, the optimized decomposition of the top quark spins above the threshold region, does not exist, and the beamline basis is the optimal basis, in which there are the dominant spin components: the up-down (UD) component for e^-le^ scattering and the down-up (DU) component for eR^-e^ scattering can make up more than 50% of the total cross section,respectively.     

Nucleon Spin Structure Functions in the Resonance Region and the Duality

We discuss the nucleon spin structure function gl and the difference between the proton and neutrontargets gp1 - gn1 , based on quark model calculation. Quark-hadron duality for the nucleon spin structure function is alsoanalyzed. Effects of the △(1232) and Roper P11(1440) resonances on the spin structure function and on the differencegn1 - gn1 are mentioned. The results of different models for the Roper resonance are also addressed.     

Playing with quantum Hall effects and single-electron-tunneling effects

The usefulness of quantum Hall effect (QHE) conductors and quantum dot (QD) devices is revealed by reviewing five remarkable effects. The first is the sensitive detection of terahertz (THz) radiation by QHE conductors. The second is the imaging of THz emission from non-equilibrium carriers in QHE conductors, by using scanning THz microscopes. The third is the single-photon detection of THz radiation in strong magnetic fields, which is carried out by incorporating a QHE electron system into a QD. Individual events of single-THz-photon absorption within the QD via cyclotron resonance cause the QD to electrically polarize, which, in turn, is detected as switches of the tunnel conductance through the QD. The fourth is the single-photon detection of THz radiation by using double QDs in the absence of a magnetic field. Both of the photon detectors are implemented in gate-voltage-induced lateral GaAs/AlGaAs QDs, and exploiting the extraordinary sensitivity of single-electron transistors to the charge. The fifth is the coherent control of nuclear spins in QHE conductors. Nuclear spins are (i) electrically polarized by unequally populating spin-split QHE edge channels via the hyperfine interaction, (ii) coherently controlled via pulsed nuclear magnetic resonance induced by local RF magnetic fields, and (iii) finally detected by the edge channels through resistance change of the Hall device. The controlled nuclear spins are limited to those along the edge channels, on the order of 10⁹.     

Dynamics of Random One-Dimensional ±J Systems

Finite chains of a two-state random Potts spin model with periodic boundary conditions are studied within Glauber dynamics. The spin exchange is assumed random with frustration between ferro and antiferromagnetic values (±J). Time-dependent fluctuations are induced by periodic temperature oscillations. Master type differential equations for spin correlation functions are solved within linear response theory. The spectrum of relaxation times are calculated at different temperatures. The ±J Potts glass chains undergo a zero temperature phase transition. The barriers against inversion of the spin chain take only two values; 0 and 2|J|. The temperature behaviour of specific heat is characterized by rounded peaks. The frequency dependence displays two plateaus for the real part of specific heat and two corresponding peaks for the imaginary part. The dynamic specific heat is not affected by the longest relaxing mode like susceptibility. The time separation of the modes is demonstrated by the Cole-Cole plots.     

Superparamagnetic relaxation Mössbauer spectra by phonon–magnon interaction using the multilevel method

The formation of local moments and the effect of charge carrriers in dilute magnetic semiconductors can be well understood using local probe techniques like Mossbauer Spectroscopy. We report here on Mossbauer studies in the systems Fe_0.008Ge_{1 ? x} D _x (D = As, Bi), Fe_0.008Ge_{1 ? x} In _x , and Fe_0.008Ge_{1 ? x} Sn _x . At room temperature magnetic interactions were observed for donor (D) impurities at the Fe site in the Fe_0.008Ge system. No such magnetic ordering was observed for acceptor (In) or neutral (Sn) impurities.     

Ab initio MRCI＋Q study on potential energy curves and spectroscopic parameters of low-lying electronic states of CS＋

Carbon monosulfide molecular ion （CS＋）, which plays an important role in various research fields, has long been attracting much interest. Because of the unstable and transient nature of CS＋, its electronic states have not been well investigated. In this paper, the electronic states of CS＋ are studied by employing the internally contracted multireference configuration interaction method, and taking into account relativistic effects （scalar plus spin–orbit coupling）. The spin–orbit coupling effects are considered via the state-interacting method with the full Breit–Pauli Hamiltonian. The potential energy curves of 18 Λ–S states correlated with the two lowest dissociation limits of CS＋ molecular ion are calculated, and those of 10 lowest Ω states generated from the 6 lowest Λ–S states are also worked out. The spectroscopic constants of the bound states are evaluated, and they are in good agreement with available experimental results and theoretical values. With the aid of analysis of Λ–S composition of Ω states at different bond lengths, the avoided crossing phenomena in the electronic states of CS＋ are illuminated. Finally, the single ionization spectra of CS （X1Σ＋） populating the CS＋（X2Σ1/2＋, A2Π3/2, A2Π1/2, and B2Σ1/2＋） states are simulated. The vertical ionization potentials for X2Σ1/2＋, A2Π3/2, A2Π1/2, and B2Σ1/2＋ states are calculated to be 11.257, 12.787, 12.827, and 15.860 eV, respectively, which are accurate compared with previous experimental results, within an error margin of 0.08 eV~0.2 eV.     

{Cu3}单分子磁体在磁场中的热纠缠

本文研究单分子磁体Na₉[Cu₃Na₃(H₂O)₉ (α-AsW₉O₃₃)₂]·26H₂O中三角自旋 环在磁场作用下的热纠缠性质, 利用数值计算求出任意两个Cu²⁺离子量子比特之间的配对纠缠度, 分别记为C₁₂, C₂₃和C₁₃. 研究结果表明, 磁场的方向和大小以及温度对配对纠缠度具有重要影响, 而且参数的变化对C₁₂, C₂₃和C₁₃的影响也是各不相同. 给出外加三个不同方向的磁场时, 配对纠缠度C₁₂, C₂₃和C₁₃各自对应的临界温度T_c随磁场强度的变化图, 由此可以得到单分子磁体三角自旋环中存在纠缠态的参数范围. 通过选择适当的磁场方向和大小以及温度等实验参数, 可以有效地调节和提高单分子磁体中的配对纠缠度. 关键词： 配对纠缠 单分子磁体 三角自旋环