Quantum Transport in Two-Dimensional Electron Systems in Super Periodic Structures

基于半导体异质界面的二维电子气，系统地研究了三角形对点晶格中的量子振荡现象。我们观察到了三种不同类型的量子干涉效应，即零场附近的Altshuler-Aronov-Spivak(AAS)振荡和Aharonov-Bohm(AB)型振荡，以及量子霍尔区的另一种AB型振荡。我们测量了它们的温度依赖关系，并阐明了退相干机制的差异。研究了介观铁磁线修饰的二维电子线在磁场空间梯度下的电子输运，发现了(1)非对称的传导和整流效应，(2)空间变化磁场中的普遍电导起伏，(3)量子霍尔区的磁势垒效应，(3)量子霍尔区的磁势垒效应(…在短周期单向横向超晶格中发现了一种新的磁阻振荡，它发生在比所谓的可公度振荡更低的磁场范围内。通过分析它与电子密度和调制周期的关系，我们得出结论，这是由于开放轨道与调制周期的几何共振所致。开放轨道是由横向超晶格的布拉格反射产生的，所以这是微小能隙形成的一个清楚的例证。通过对磁阻可公度性振荡的分析，建立了在二维平面上量化调制幅度的方法。研究了空间交变磁通模式下超导导线网络的Little-Parks振荡。振荡模式随交变场和均匀场振幅的演化与相应霍夫斯塔特蝴蝶的光谱边缘很好地吻合。较少

We carried out a systematic study of quantum oscillatory phenomena in triangular antidot lattices based on two-dimensional electron gas(2DEG) at semiconductor heterointerface. We have observed three different types of quantum interference effects, ---Altshuler-Aronov-Spivak(AAS) oscillation and Aharonov-Bohm(AB) type oscillation near zero field and another type of AB-type oscillation in the quantum Hall regime. We measured their temperature dependences, and elucidated the differences in the decoherence mechanisms. The gate bias dependence of the high field AB-type oscillation furnished information on the self-consistent screened potential formed around the antidots.We studied electron transport under spatial gradient of magnetic field in 2DEG quantum wire decorated with mesoscopic ferromagnetic wire, and found (1)asymmetric conduction and rectifying effect, (2)universal conductance fluctuation in spatially varying magnetic field, and (3)magnetic barrier effect in the quantum Hall regim … More e.We have uncovered a novel magnetoresistance oscillation in short period unidirectional lateral superlattices, which occurred in the lower magnetic field range than the so-called commensurability oscillations. From the analysis of its dependence on the electron density and modulation period, we concluded that the phenomenon is due to geometrical resonance of open orbits with the modulation period. The open orbits are created by Bragg reflection from the lateral superlattice, so this is a clear demonstration of the mini-gap formation. We have also established the method to quantify the modulation amplitude at the 2DEG plane from the analysis of the commensurability oscillation of magnetoresistance.The Little-Parks oscillation of a superconducting wire network subjected to a spatially alternating magnetic flux pattern was investigated. The evolution of the oscillation pattern as a function of the amplitude of the alternation field and that of the uniform field was shown to agree well with the spectral edge of the corresponding Hofstadter butterflies. Less