金属双层膜中量子输运的表面和界面散射效应

运用格林函数的解析方法研究金属双层膜的电子输运.考虑了量子尺寸效应和来自杂质、粗糙表面和粗糙界面三方面的散射,计算单粒子格林函数和平行电导率,得到了金属双层膜的电导公式.计算结果表明,在薄膜极限和表面及界面散射的最低阶近似下,系统总电导率等于各子能级通道的电导率之和,而各子能级通道中杂质、表面和界面产生的散射率是可相加的. 关键词：     

磁多层金属系统的界面反射效应

考虑到磁多层金属系统中的粗糙界面散射效应,运用量子统计的格林函数方法和久保理论,计算磁多层金属系统的单粒子传播格林函数和电导率.所得结果依赖于电子在界面处的反射波幅和空间尺寸,并能展示巨磁电阻的主要实验特征. 关键词：     

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.     

金属薄膜的量子输运理论

运用格林函数方法和久保公式研究金属薄膜中的电子输运．考虑了量子尺寸效应及来自杂质和两个粗糙表面的散射，计算单粒子格林函数和平行电导率．计算结果表明：（1）在薄膜系统中，电子数密度、平均自由程以及来自杂质和表面散射的电导率都以π/k_F（k_F为费密波矢的数值）为周期随厚度d振荡；（2）在薄膜和厚膜的两种极限、以及取表面粗糙度的最低阶近似下的结果可以推出用半经典和量子方法所得的金属薄膜的电导公式 关键词：     

磁性多层薄膜系统中的巨磁电阻效应

考虑到量子尺寸效应以及来自杂质、粗糙表面、粗糙界面三方面的散射,运用量子统计格林函数方法和久保理论,计算了磁性多层薄膜系统中的巨磁电阻,讨论了巨磁电阻随非磁层厚度作周期性振荡,以及在(Fe/Cr)_N/Fe系统中巨磁电阻随多层基元数目N增加而增大等现象.理论计算与实验结果符合.此外,还讨论了有关各种散射引起的散射率能否相加的问题. 关键词：     

大尺度分层介质粗糙面电磁散射的特性研究

首先建立大尺度分层介质粗糙面散射的物理模型, 基于Stratton-Chu积分方程和Kirchhoff近似导出了粗糙面散射场的计算公式. 采用高斯随机粗糙面来模拟实际的分层介质粗糙面, 通过数值计算得到了正下视单站雷达接收到的后向散射回波. 理论推导了散射场强度与表面粗糙度之间的定量关系, 并从数值仿真的角度分析了表面和次表面的粗糙度对散射回波的影响, 给出了散射场随粗糙度变化的曲线. 最后考察了分层介质的电特性参数(介电常数和电导率)对分层粗糙面散射场的影响, 并对计算结果做出了分析.     

分子（H2,D2）与固体表面散射的理论研究

在含时量子计算方法的基础，利用量子散射中的角动量耦合理论等，导出了分子与固体表面非弹性散射的计算公式，对分子（Ｈ２，Ｄ２）与粗糙固体表面在较低能量下的非弹性散射做了计算，得出了模型势下的散射规律。     

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     

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：     

二维无序电子系统子带间的杂质散射效应

借助于格林函数方法,研究了二维无序电子系统子带间杂质散射对电导率和霍耳系数的量子相干修正的影响。结果表明当电子从单带占据过渡到双带占据时,电导率和霍耳系数均发生跨越行为。 关键词：     

Quantum Analytical Theory for Giant Magnetoresistance in Magnetic Multilayered Cylindrical Systems

Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces,we use quantum-statistical Green‘s function approach and Kubo theory to calculate the electronic conductivity and the giant magnetoresistance in magnetic multilayered cylindrical systems.It is found that in the limit of weakly scattering from impurities surface and interfaces,the total conductivity is given by a sum of conductivities of all the subbands and two spin-channels.For each subband and each spin-channel the scattering rate due to the impurities,surface and interfaces is added up.     

Influence of Interface Scattering and Quantum Size Effect on the Giant Magnetoresistance in a Magnetic Sandwich Structure

An analytical Green's function approach to the study of the electronic transport in a magnetic sandwich structure is presented. Taking into account the quantum size effect and considering three types of scattering from bulk impurities, rough surface, and two rough interfaces, we calculate the one-particle Green's function and the in-plane conductivity, yield a new formula for conductivity. It is found that (i). the magnetoresistance in the ultrathin spin-value sandwiches shows oscillation as a function of thickness with a period of half Fermi wavelength; (ii) in the thin-film limit and the lowest-order approximation of the surface and interface scatterings, the total conductivity is given by a sum of conductivities of all the subbands and the two spin channels, for each subband and each spin channel the scattering rates due to the impurities, surfaces and interfaces are additive.     

Quantum analytical theory for giant magnetoresistance in magnetic multilayered film systems

Taking into account the quantum size effects and considering three types of scattering from bulk impurities, rough surfaces, and rough interfaces, we use the quantum-statistical Green's function approach and Kubo theory to calculate the giant magnetoresistance (GMR) in magnetic multilayered structures. Our calculation can reproduce the main features of GMR experiments, including the oscillations of GMR with nonmagnetic thickness, and the GMR increases with increasing number of bilayers N of the (Fe/Cr)_N/Fe system and others. As well, the question whether or not the scattering rates due to the impurities, surfaces, and interfaces add up is also addressed to.     

Green’s function approach to transport in quantum wires with rough surfaces

By including the scattering from bulk impurities and rough surface, a Green’s function approach to transport in a quasi-one-dimensional cylindrical wire is presented. Taking into account the quantum size effects (QSE), we calculate the one-particle Green’s function and the electrical conductivity along a quantum wire, yielding a new formula for the conductivity in quantum wires. It is shown that the conductivity exhibits certain oscillation in the region of very small radius of wires where the QSE are manifestly important, and its envelope decreases with decreasing the radius.     

Thermal conductivity of VLS-grown rough Si nanowires with various surface roughnesses and diameters

In this paper, we synthesize VLS-grown rough Si nanowires using Mn as a catalyst with various surface roughnesses and diameters and measured their thermal conductivities. We grew the nanowires by a combination vapor-liquid-solid and vapor-solid mechanism for longitudinal and radial growth, respectively. The surface roughness was controlled from smooth up to about 37 nm by the radial growth. Our measurements showed that the thermal conductivity of rough surface Si nanowires is significantly lower than that of smooth surface nanowires and decreased with increasing surface roughness even though the diameter of the smooth nanowire was lower than that of the rough nanowires. Considering both nanowires were grown via the same growth mechanism, these outcomes clearly demonstrate that the rough surface induces phonon scattering and reduces thermal conductivity with this nanoscale-hole-free nanowires. Control of roughness induced phonon scattering in Si nanowires holds promise for novel thermoelectric devices with high figures of merit.