正常金属-铁磁绝缘层-d波超导结中的磁散射对量子输运的影响

在正常金属-铁磁绝缘层-d波超导隧道结中,考虑到铁磁绝缘层的粗糙界面散射和磁散射效应,运用Bogoliubov-de Gennes(BdG)方程和Blonder-Tinkham-klapwijk(BTk)理论模型,计算隧道结中的准粒子传输系数和微分电导.计算表明：1)粗糙界面散射和磁散射都能压低零偏压电导峰,其中磁散射能使零偏压峰滑移,而粗糙界面却能阻止零偏压峰的滑移,且随着两种散射强度的逐渐增大,又能使零偏压电导峰渐渐变为凹陷;(2)当铁磁层离开超导表面有若干相干长度时,隧道谱中将呈现一些子能隙谐振峰. 关键词：     

铁磁-d波超导结中的自旋极化隧道谱

考虑到铁磁层中准粒子输运的自旋极化效应以及 d波超导表面时间反演对称态的破缺效应 ,在 Blonder-Tinkham-Klapwijk散射理论框架下 ,研究铁磁 -d波超导隧道结中的隧道谱 ,所得结果能展示一些新奇特征 ,并能解释一些实验现象     

正常金属-铁磁绝缘层-dx2-y2+idxy混合波超导结中的磁散射对隧道谱的影响

在正常金属铁磁绝缘层dx2-y2 idxy混合波超导隧道结中,考虑到铁磁绝缘层的磁散射和界面的粗糙散射效应,运用BogoliubovdeGennes(BdG)方程和BlonderTinkhamKlapwijk(BTK)理论,计算了隧道结中的准粒子传输系数和微分电导.研究表明:(1)磁散射和界面粗糙散射均可以压低电导峰,其中磁散射能使电导峰滑移,而粗糙界面散射却能阻止这种滑移,且两散射的共同作用可抑制由混合波两序参数的幅值比不同所导致的电导峰滑移;(2)随铁磁层离超导表面距离的增加,隧道谱在零偏压处由凹陷变成了零偏压电导峰,继而又演化为凹陷中的中心峰;(3)当铁磁层离开超导表面有若干相干长度时,隧道谱中将呈现一些子能级谐振峰.     

铁磁-d波超导结中的粗糙界面散射和自旋反转效应对隧道谱的影响

考虑到铁磁层中的自旋极化效应、以及界面的粗糙散射和自旋反转效应,利用推广了的Blonder Tinkham Klapwijk理论模型,计算铁磁d波超导结中的自旋极化隧道谱.研究表明1)自旋反转效应能使零偏压电导峰变得尖锐;2)粗糙的界面散射除了能压低零偏压电导峰的高度,还能使零偏压凹陷处感应出一中心峰.结果能定性地解释最近的两篇关于La_2/3Ba_1/3 MnO₃/DyBa₂Cu₃O_{7关键词： 自旋极化效应 自旋反转效应 粗糙界面散射效应 隧道谱}     

N/I/d波超导体结中的准粒子非弹性散射效应

考虑准粒子的非弹性散射和正常金属区域的杂质散射,以方势垒描述N/I/d波超导体结中绝缘层对准粒子输运的影响,运用Bogoliubov-de Gennes(Bde)方程和Blonder-Tinkham-Klapwijk(BTK)理论,计算了N/I/d波超导体结的隧道谱.研究表明;(1)伴随着准粒子的非弹性散射效应,绝缘层的势垒值及绝缘层厚度对零偏压电导峰值有显著影响;(2)准粒子有限寿命的缩短,可压低零偏压电导峰,并抹平能隙处的小峰或凹陷;(3)较大的杂质散射会导致零偏压电导峰的劈裂,而准粒子的非弹性散射则可有效地阻止其劈裂.     

正常金属/铁磁绝缘层/p波超导体结的隧道谱

利用Blonder-Tinkham-Klapwijk理论,计算了正常金属/铁磁绝缘层/p波超导体结的隧道谱.结果表明:(1)在正常金属/铁磁绝缘层/p波超导体结的隧道谱中存在零偏压电导峰、零偏压电导凹陷;(2)在Px波结的隧道谱中,磁散射能导致零偏压电导峰的劈裂,而界面的粗糙散射却可以阻止其劈裂;(3)界面的势垒散射,磁散射及其与粗糙散射的共同作用对px、py波结零偏压电导的影响是不同的.     

正常金属/dx2-y2+idxy混合波超导隧道结中的微分电导

运用Bogoliubov-de Gennes(BdG)方程和Blonder-Tinkham-Klapwijk(BTK)理论,计算了正常金属/dx2-y2 idxy混合波超导隧道结中的准粒子输运系数和微分电导.研究表明:(1)影响电导谱中零偏压电导峰滑移的因素有杂质散射、dxy波分量、混合波两分量的强度比、界面的势垒散射强度、超导晶轴方位等,其中d-xy波分量的存在和超导晶轴方位是关键因素;(2)在θ=π/4的情况下,零偏压电导峰出现的条件为Δ2=0或α=nπ/4;(3)粒子的入射角对电导峰的高低有显著影响.     

正常金属-d波超导隧道结中杂质和界面散射对微分电导的影响

考虑到正常金属区域的杂质散射和界面粗糙的散射,运用Bogoliubov-de Gennes (BdG)方程和Bolonder-Tinkham-Klapwijk(BTK)理论模型,计算正常金属-d波超导隧道结的微分电导.计算发现：隧道谱强烈地依赖电子的入射角和超导体晶轴方位,并能展示零偏压电导峰的存在;此外,杂质散射能使隧道谱的凹陷分裂出两个小凹陷,而界面粗糙能抹平和压低零偏压电导峰和能隙电导峰.这些结果都将很好地解释高T_c超导隧道谱的实验现象. 关键词：     

铁磁绝缘层对正常金属/铁磁绝缘层/正常金属/p波超导结隧道谱的影响

在正常金属/铁磁绝缘层/正常金属/自旋三重态p波超导隧道结中,考虑到铁磁绝缘层的磁散射和粗糙界面散射,运用Bogoliubov-de Gennes(BdG)方程和Blonder-Tinkham-Klapwijk(BTK)理论模型,研究了铁磁绝缘层对隧道结微分电导的影响.研究表明:(1)对于px波,粗糙界面散射和磁散射都能使零偏压电导峰变低,能隙处凹陷升高;随着磁散射的增强,谱线的尖锐峰消失,宽峰逐渐变为凹陷;(2)对于py波,粗糙界面散射和磁散射都能使零能凹陷上移,能隙峰变低,随着粗糙界面散射的增强,两能隙峰间距减小;随着中间正常金属层厚度的增加,能隙内电导随外加偏压呈现振荡行为,能隙外电导仅与普通势垒有关;(3)对于px+ipy波,随着粗糙界面散射的增强,零偏压电导峰被压低,双凹陷处的值逐渐增大为小的能隙峰,而磁散射并不改变谱线中各凹陷处的电导值.     

正常金属—d波超导隧道结中杂质和界面散射对微分电导的影响

考虑到正常金属区域的杂质散射和界面粗糙的散射,运用Ｂｏｇｏｌｉｕｂｏｖ－ｄｅ Ｇｅｎｎｅｓ（ＢｄＧ）方程和Ｂｏｌｏｎｄｅｒ－Ｔｉｎｋｈａｍ－Ｋｌａｐｗｉｊｋ（ＢＴＫ）理论模型,计算正常金属－ｄ波超导隧道结的微分电导。计算发现：隧道谱强烈地依赖电子的入射角和超导体晶轴方位,并能展示零偏压电导峰的存在;此外,杂质散射能使隧道谱的凹陷分裂出两个小凹陷,而界面粗糙能抹平和压低零偏压电导峰和能隙电导峰。这些     

核磁共振碳谱研究:烷烃化学位移和(CSS)与分子路径指数矢量(VPM)

系统研究了核磁共振碳谱和化学位移规律及其定量构谱关系(QSSR).本文研究了一组十元素分子路径指数矢量VPM,并发现它与烷烃化学位移和CCS有良好线性相关性.采用多元线性回归进行准确估计与预测,结果优良.     

稠苯芳杂环及其烷基质子化学位移的计算

本文提出了予测稠苯芳杂环及其烷基链上质子化学位移的计算方法。 将稠苯芳杂环化合物用凯库勒式表示,计算式为为需考虑的苯环内的乙烯基效应。σ_mi,ci为各苯环的环流效应。σ_1,Hc为各芳杂环的屏蔽效应,对杂环上质子它就是该单独芳杂环上相应质子的δ值,对苯环上质子要将它分解为各结构因素的效应,即:σ_1,He=(1/2)^d-1δ_x=y(或σ_z)+σ_c-c·σ_m,H. σ_x-y与σ_z为杂原子或其基团的屏蔽效应,σ_c=c为存在于芳杂环中的乙烯基的效应,σ_m,Hc为芳杂环的环流效应,d为对不同质子所考虑的键数。有取代基时需考虑取代基的效应。计算环上烷基质子的公式为:δ=σ_p,CH3+ασ_c,CH3+βσ_t,CH3+σ_l,G σ_l,G为稠苯芳杂环基的某级效应。     

Reduced s-d model with antiferromagnetically coupled impurity spins

An antiferromagnetic equivalent-neighbour Heisenberg interaction H_i between impurity spins is added to the reduced s-d Hamiltonian H_r previously introduced by simplifying the Kondo s-d exchange Hamiltonian H_K. Asymptotic mean-field theory is developed for H_r + H_i, in the presence and absence of external magnetic field, and applied to (La_1−xCe_x)Al₂ alloys. Specific heat c_i(T) and zero-field susceptibility χ_i(0,T) curves for (La_1−xCe_x)Al₂ are depicted. The coupling constants of H_r + H_i and conduction bandwidth are adjusted so that T_c temperatures for x = 0.2, 0.1 are equal to the experimental values. c_i(T) exhibits a jump at T_c and is decreasing for T < T_c. χ_i(0,T) has a first order pole at T_c which corresponds to the maximum of experimental susceptibility and χ_i(0,0) > 0. These results improve those obtained earlier on the grounds of H_r theory.     

Interrelations of discrete Painlevé equations through limiting procedures

We study the discrete Painlevé equations associated to the affine Weyl group which can be obtained by the implementation of a special limits of -associated equations. This study is motivated by the existence of two -associated discrete both having a double ternary dependence in their coefficients and which have not been related before. We show here that two equations correspond to two different limits of a -associated discrete Painlevé equation. Applying the same limiting procedures to other -associated equations we obtained several -related equations most of which have not been previously derived.     

Structural phase transitions at clean and metal-covered Si(111) surfaces investigated by RHEED spot analysis

Structural phase transitions between various kinds of superlattice structures formed on a Si(111) surface have been investigated by spot analysis of reflection high-energy electron diffraction (RHEED). Reversible transitions induced by temperature changes and irreversible ones induced by metal depositions were observed. Detailed discussions on the dynamics of the phase transitions are made by quantitative analyses of integrated spot intensity and profile. For a phase transition of 7′7  1′1 structures on a clean Si(111) surface, a hysteresis with temperature difference of 5°C. between in heating and cooling processes was found in the spot intensity change, indicating a first-order transition. Hysteresis was hardly recognized, on the other hand, for transitions of Au-induced superstructures (5×2-Au or ×-Au)  1×1-Au. The spot profiles were found to be broadened during the transition of Si(111)-×-Au  1×1-Au, which was a signature of a continuous transition, while the profiles remained unchanged during the transitions of the 7×7  1×1 and 5×2-Au  1×1-Au phases. Structural conversions induced by In adsorption on the Si(111) surface kept at constant temperatures were also analyzed. The conversions at room temperature were totally dependent on the initial substrate surface structures; the 7×7 surface did not show any structural conversion with In adsorption, while the ×-In surface successively converted to a 2×2 and a × phase with coverage increase. The structural transitions at elevated temperatures were sensitively dependent on the temperatures. Sequences of transitions among the 7×7, 4×1, ×, 1×, and ×4 were quantitatively revealed as changes in RHEED spot intensity.     

ErP5O14非晶玻璃的红外量子剪裁

研究了Er_1.0P₅O₁₄铒非晶玻璃的红外量子剪裁现象. 从吸收谱和激发光谱的计算比较中肯定了Er_1.0P₅O₁₄非晶 玻璃的1537.0 nm红外荧光为多光子量子剪裁荧光. 从Er_1.0P₅O₁₄非晶玻璃的可见和红外荧光发射光谱中发现激发²H_11/2, ⁴G_11/2和⁴G_9/2能级所导致的⁴I_13/2→⁴I_15/2量子剪裁红外荧光很强;基于自发辐射速率、无辐射弛豫速率和能量传递速率等参数的计算,对其量子剪裁机理进行了分析.发现起源于基态的强下转换能量传递{²H_11/2→⁴I_9/2,⁴I_15/2→⁴I_13/2},{⁴G_11/2→⁴I_13/2, ⁴I_15/2→²H_11/2},{⁴G_9/2→⁴F_7/2,⁴I_15/2→⁴I_13/2}和{⁴G_9/2→⁴I_13/2, ⁴I_15/2→²H_11/2}是导致Er_1.0P₅O₁₄非晶玻璃具有强的三光子和四光子量子剪裁红外荧光的原因.研究结果对改善太阳能电池效率有一定意义.     

The ΔNγ electromagnetic transition form factors GM(q) and GE(q)

A parameter-free, nonperturbative calculation of the ΔNγ electromagnetic transition amplitudes GM*(q2), GE*(q2), and the resonant multipole ratio REM(q2)≡E1+3/2(q2)/M1+3/2(q2) is performed in terms of the well-known nucleon isovector Sachs form factor GMV. Our methods are fully relativistic with conservation of the electromagnetic current guaranteed. We find that GM*(q2) decreases more rapidly than the nucleon dipole form factor when −q21 GeV2/c2 and that REM(q2) remains small even for very high four-momentum transfer implying that the perturbative QCD prediction REM(q2)→1 is purely asymptotic and is valid only for extremely high |q2|.