一维准周期晶格中玻色子对的迁移率边

研究了一维非公度的准周期晶格中的玻色子对的迁移率边.通过微扰方法,解析推导出强相互作用极限下准周期晶格中玻色子对迁移率边的解析表达式,通过数值证明在系统参数b较小时,迁移率边的解析结果符合得较好,而当b→1时,解析结果将发生偏离.     

一维无公度势系统的迁移率边

“相继平均电阻率”局域性判据被用于研究一维无公度势体系Soukoulis-Economou模型的电子态局域性。本文所采取的数值计算方法表明,在波矢Q=0.7时中间三个子带的所有电子态均是扩展态,并未发现所谓的“局部迁移率边”。 关键词：     

水溶液中稀土离子与甘氨酸、丝氨酸、天冬氨酸作用的13C NMR研究

测定了酸性水溶液中甘氨酸、丝氨酸和天冬氨酸稀土络合物(Ln=La、Pr、Nd、Eu、Tb、Dy、Ho、Er、Tm和Yb)的¹³C诱导位移。对位移试剂的分析指出,三种氨基酸通过α-羧基以双齿形式配位于稀土,配位键长为0.23nm~0.25nm,天冬氨酸的γ-羧基也是配位基团。由本文与文献中已报道的各种氨基酸稀土络合物的¹³C诱导位移的系统分析表明,配体¹³C超精细偶合常数A值和结构因子G值有如下规律:(1)│A(C₀)│<│A(C_α)│;A(C₀)为正,A(C_α)为负;(2)│G(C₀)│>│G(C_α)│;配体碳核的G均为负值。     

方波驱动法测定Alq3的电子迁移率

在非正弦波(方波)的驱动下,观察到了OLED中Alq₃的电致发光现象。在高段方波驱动下,Alq₃中的电子向阳极移动;在低段方波驱动下,Alq₃中的电子向阴极移动。当方波的周期是电子穿过Alq₃中所用时间的2倍时,Alq₃中的电致发光现象完全消失。由此,可以计算出Alq₃中的电子迁移率,得到的结果和文献的报道值相吻合。对Alq₃中电子迁移率和厚度的关系进行了研究,从而提出了一种简单易行的计算有机材料的电子迁移率的方法。     

Sr原子里德伯态的|ml|相关场电离阈

用偏振激光两步激发,获得不同│m_l│值的里德伯态,在2.4kV/cm以下的电场范围内,测定了Sr原子5snd(n=22-27),│m_l│=0,1,2各里德伯态的电离阈值。理论给出了二阶近似下│m_l│有关的电离阈,并与测量结果作了对照。 关键词：     

低插损微小型表面漏波谐振滤波器

本文的工作在于,利用49°Y旋转铌酸锂基片,在其基片的表面激励表面漏波,利用其机电耦合系数k_s~2比较高;短路金属反射条声阻抗变化比较大的特点,成功地研制了表面漏波谐振滤波器(Surface Leaky waves resonators简称SLWR)。这种谐振滤波器的突出优点是所占的基片面积小,仅为同频率的声表面波谐振滤波器(SAWR)的1/4—1/5,50Q系统中的插入损耗仅2—5dB。 本文在实验上,测定了49°Y旋转LiNbO_3基片表面的机电耦合系数k_s~2及声阻抗失配比│8│,从而计算了不同短路金属反射条时的反射系数。利用等效电路模型定性分析了它在50Q系统中的插入损耗。并介绍了典型的实验数据。     

DNA平衡离子凝聚的动态光散射分析

利用动态光散射技术系统地研究了不同化合价的平衡离子氯化钠 (Na⁺)、氯化镁 (Mg²⁺)、三氯六氨络合钴 ([Co(NH₃)₆]³⁺) 和精胺 ([C₁₀N₄H₃₀]⁴⁺) 与DNA之间的相互作用. 实验结果显示, 当缓冲液中只包含Na⁺ 或Mg²⁺, 且浓度c≥ 5 mM时, DNA电泳迁移率之比约为2:1; 当缓冲液单独包含Na⁺或[Co(NH₃)₆]³⁺, 且浓度c≥ 5 mM时, DNA 的电泳迁移率之比约为4.5:1. 而当平衡离子的化合价为4时, 观察到DNA的电泳迁移率由负变正, 意味着发生了电荷反转. 在平衡离子浓度c<5 mM时, 随着离子浓度的增大, 迁移率之比逐渐增大. 对于一价或二价平衡离子情形, 实验结果与Manning的平衡离子凝聚理论的预言相符. 对于三价平衡离子, 实验结果与理论值有明显偏离. 而对于四价离子, 由于发生了DNA电荷逆转, 基于平均场的平衡离子凝聚理论失效. 另外, 通过原子力显微镜观察到当平衡离子的化合价大于等于3 时, DNA分子的构型发生变化. 因此, 自由溶液中的聚电解质的构型和离子关联效应在聚电解质迁移过程中起重要作用. 关键词： 电泳迁移率 平衡离子 动态光散射 DNA     

基于WS2可饱和吸收体的脉冲激光器研究

利用WS₂的可饱和吸收特性,在激光二极管侧面抽运Nd:YAG固体激光器Z型腔结构中分别实现了被动调Q和被动调Q锁模运转。实验表明:当泵浦电流为9.5 A时,开始启动调Q运转,当泵浦电流大于9.8 A时,调Q激光脉冲趋于稳定。当泵浦电流为12.8 A时,被动调Q输出的最大平均功率为466 mW,最窄脉冲宽度为3.205 μs,对应的重复频率为71.70 kHz,此时最大单脉冲能量为6.5 μJ。当泵浦电流达到13.4 A时,激光器实现调Q锁模运转。调Q锁模的最高输出功率为590 mW,调Q包络频率为71.98 kHz,单个调Q包络内的脉冲串重复频率123.1 MHz,每个调Q包络中包含369个脉冲,单脉冲能量为22.2 nJ。结果表明WS₂材料可以作为可饱和吸收体用于固体激光器中。     

应变Si/(001)Si1-xGex电子迁移率

依据离化杂质散射、声学声子散射和谷间散射的散射模型,在考虑电子谷间占有率的基础上,通过求解玻尔兹曼方程计算了不同锗组分下,不同杂质浓度时应变Si/(001)Si_1-xGe_x的电子迁移率.结果表明:当锗组分达到0.2时,电子几乎全部占据Δ₂能谷;低掺杂时,锗组分为0.4的应变Si电子迁移率与体硅相比增加约64%;对于张应变Si NMOS器件,从电子迁移率角度来考虑不适合做垂直沟道.选择相应的参数,该方 关键词： 电子谷间占有率 散射模型 锗组分 电子迁移率     

超导弱连接中的Josephson电流在一个磁通量子内的振荡(Ⅰ)——Josephson结

本文指出如果Josephson结处在Q值足够高的谐振腔内,当Josephson频率ω=(2eV₀)/h与谐振腔的本征频率ω_r发生谐振时,谐振的电磁场对Josephson结自身的反馈作用将导致超流电流在一个磁通量子内随磁场的小周期振荡。 关键词：     

一维无公度体系的电子谱和迁移率边

本文详细地计算了对角元为1.9[cos(0.7n)+1/3cos(1.4n)]、非对角H_n,n+1=H_n,n-1=1的一维无公度模型的电子态密度,用自能收敛性判据确定出迁移率边的精确位置,讨论了电子谱与迁移率边的自相似性。 关键词：     

Possible evidence for an incommensurate spin density wave in the stanford electron tunneling studies into LaSrCuO

The Stanford studies include a remarkable dI/dV versus voltage curve with not just one BCS-like peak on each of the positive and negative voltage curves, but with three peaks on the positive-V side, and almost the same structure on the negative-V side. This structure may be caused by an incommensurate spin density wave (SDW) with T_CSCW comparable to 125 K. Incommensurability of the SDW would replicate the usual structure at E_F with two peaks at the edges of a 2Δ gap centred not at E_F, but at displaced positions ± 2v_FδQ away from E_F, where δQ is the incommensurability of the SDW wave vector.     

一类一维势场中电子态的研究

研究了在一维势场Ｖ_n＝λｃｏｓ（Ｑn＋ａｎ^ｖ）（０＜ｖ＜１）中运动的电子状态，计算了本征能量和本征态的局域化指数。对Ｑ＝２π／３，系统的能带由三个子能带构成。当λ小于２时，每个子带中有两个迁移率边界。研究了扩展态、局域态以及迁移率边界随参数λ，ν，α的变化。 关键词：     

The effect of SiO2 buffer layer on the electrical and structural properties of Al-doped ZnO films deposited on soda lime glasses

In this paper, the influence of SiO₂ buffer layer on electrical and structural properties of AZO films on soda lime glasses has been investigated. The results showed that the Hall mobility and carrier concentration of AZO films deposited on soda lime glasses at high temperature could be enhanced by introducing SiO₂ layers. The optical absorption edges of AZO films with SiO₂ buffer layer are blue shifted compared with that of buffer layer free due to the increase of carrier concentration. SiO₂ layers prepared at 400 °C more effectively suppress the diffusion of Na atoms into AZO films compared with that prepared at room temperature. On the other hand, the in-plane stress dependence of optical band gap is linear for AZO films deposited on quartz glass substrates, but is deviated from linearity in the case of soda lime glass substrates.     

Dependence of current on energy for the integral quantum Hall effect

The dependence of the Hall-current on energy of a 2-D electron system in a strong perpendicular magnetic field is studied using sum rule arguments. It turns out that, in a finite system, this dependence is determined to a large extent by the states at the edges of the system. As a consequence the distance between the mobility edges is considerably smaller than the width of the density of states. In fact the mobility edges are essentially the same as in the unperturbed system.     

EDTA辅助水热合成FeS2/NiSe2复合纳米晶及其薄膜光电性质

以EDTA为螯合剂，加入MX2结构化合物NiSe₂作为晶种，水热合成了FeS₂纳米晶. x射线衍射分析结果表明产物为单一相黄铁矿型FeS₂（pyrite）,平均粒径约40—50nm.丝网印刷成膜且高温退火后FeS₂薄膜光学直接带隙变宽.随晶种量的增加，吸收边在紫外—可见光谱区红移、方块电阻升高、霍尔迁移率上升和载流子浓度下降，实现了n型掺杂.并且对FeS₂的形成机理进行了讨论. 关键词： 2纳米晶')" href="#">FeS₂纳米晶 水热 诱导结晶 直接禁带宽度      

Almost mobility edges and the existence of critical regions in one-dimensional quasiperiodic lattices

We study a one-dimensional quasiperiodic system described by the Aubry–André model in the small wave vector limit and demonstrate the existence of almost mobility edges and critical regions in the system. It is well known that the eigenstates of the Aubry–André model are either extended or localized depending on the strength of incommensurate potential V being less or bigger than a critical value V _c , and thus no mobility edge exists. However, it was shown in a recent work that for the system with V < V _c and the wave vector α of the incommensurate potential is small, there exist almost mobility edges at the energy E _c±, which separate the robustly delocalized states from “almost localized” states. We find that, besides E _c±, there exist additionally another energy edges E _c′±, at which abrupt change of inverse participation ratio (IPR) occurs. By using the IPR and carrying out multifractal analyses, we identify the existence of critical regions among |E _c±|?≤?|E|?≤?|E _c′±| with the mobility edges E _c± and E _c′± separating the critical region from the extended and localized regions, respectively. We also study the system with V > V _c , for which all eigenstates are localized states, but can be divided into extended, critical and localized states in their dual space by utilizing the self-duality property of the Aubry–André model.     

Bi2Sr2CaCu2O8 crystal with a region of periodic blind antidots – transition between bulk and interface vortex pinning

This work focuses on differential magneto-optical two-dimensional imaging of the current distribution in a high-T_c superconducting Bi₂Sr₂CaCu₂O₈ crystal having a region of 170 × 170 μm² patterned with periodic blind antidots. By measuring the self-induced field of an applied current, we can map the current flow distribution within and at the edges of the patterned region. We detected three separate types of current flow within the patterned region, which correspond to three different arrangements of pancake vortices within and at the edges of the patterned region. At high temperatures the vortices delocalize from the antidots, presumably due to thermal fluctuations. However, at lower temperatures vortex pinning mechanisms become prominent, lowering the vortex mobility in the patterned region. There are two contributing mechanisms: bulk pinning by the patterned antidots and interface pinning due to an entry barrier into the patterned region. Each mechanism is dominant at different temperatures. From our experiments we see that the T–H transition line from the bulk to the interface pinning and the vortex melting line in the pristine region coincide.     

Quantum discord and classical correlation signatures of mobility edges in one-dimensional aperiodic single-electron systems

We investigate numerically the quantum discord and the classical correlation in a one-dimensional slowly varying potential model and a one-dimensional Soukoulis–Economou ones, respectively. There are well-defined mobility edges in the slowly varying potential model, while there are discrepancies on mobility edges in the Soukoulis–Economou ones. In the slowly varying potential model, we find that extended and localized states can be distinguished by both the quantum discord and the classical correlation. There are sharp transitions in the quantum discord and the classical correlation at mobility edges. Based on these, we study “mobility edges” in the Soukoulis–Economou model using the quantum discord and the classical correlation, which gives another perspectives for these “mobility edges”. All these provide us good quantities, i.e., the quantum discord and the classical correlation, to reflect mobility edges in these one-dimensional aperiodic single-electron systems. Moreover, our studies propose a consistent interpretation of the discrepancies between previous numerical results about the Soukoulis–Economou model.