Study of Quantum Transport in Low Dimensional Electrons in Superperiodic Structures

能带理论构成了固体物理的基础，本质上是对电子在周期势中的行为的描述。在这个研究项目中，我们研究了起源于超周期结构的输运现象。所研究的材料包括有机导体、石墨层间化合物、半导体超晶格和金属多层膜等天然和人工铺设材料。我们还研究了具有微结构栅电极的半导体界面的二维电子系统。用这笔赠款购买的超导磁体系统也被有效地应用于稀磁半导体的研究。主要研究成果如下：通过在表面制备微结构铁磁栅电极的GaAs/AlGaAs异质结，成功地将空间调制磁场应用于二维电子气。我们早些时候预测，在磁场的单向调制下。磁阻表现出可公度性振荡效应。角相关磁阻振荡(ADMRO)是在(BEDT-TTF)基有机导体中发现的一种现象。我们从理论上证明了它是准二维费米面的一种普遍性质，并通过观察石墨层间化合物和GaAs/AlGaAs超晶格中的ADMRO从实验上证实了这一点.(BEDT-TTf)2KHg(SCN)4表现出一种不同类型的ADMRO.通过两轴旋转测量的电阻率倾角的映射和模型计算，阐明了它起源于准一维费米面上开放轨道与底层单胞的可公度性.

The band theory which constitutes the basis of solid state physics, is essentially a description of the behavior of electrons in periodic potential. In this research project, we have investigated transport phenomena that originate from superperiodic structures. The materials investigated are natural and artificial layred materials including organic conductors, graphite interacalation compounds, semiconductor superlattices and metallic multilayrs. We also studied two-dimensional electron system at the interface of semiconductors with microstructured gate electrode. The superconducting magnet system purchased with this grant has been also effectively used in studies of diluted magnetic semiconductors.The followings are the main research acomplishments :By fabricating GaAs/AlGaAs heterostructures with microstructured ferromagnetic gate electrode on the surface, we have succeeded in applying spatially modulated magnatic field to two-dimensional electron gas. We predicted earlier that in a unidirectional modulation of magnetic field. the magnetoresistance shows commensurability oscillation effect. which we have experimentally verified in this research term.Angular-dependent magnetoresistance oscillation (ADMRO) is a phenomenon discovered in (BEDT-TTF)-based organic conductors. We have shown theoretically that it is a generic property of quasi-two-dimensional Fermi surface, and experimentally verified it by observing the ADMRO in graphite intercalation compounds and also in GaAs/AlGaAs superlattice.(BEDT-TTF)2KHg(SCN)4 exhibits a different type of ADMRO.We have clarified that it originates from the commensurability of open orbits on a quasi-one dimensional Fermi surface with the underlying unit cell by mapping of the resistivity dips from two-axis rotation measurement and by model calculations.