Imaging of electron spin density in coupled semiconductor nanostructures at^3 He temperatures

半导体纳米结构的一大优点是可以人为地设计电子态和自旋态。这使我们能够在半导体纳米结构中制备出具有新颖物理特性的电子态。本研究的目的是在外部可控的半导体纳米结构中检测新的相关电子态。研制了低温强磁场下空间分辨圆极化光谱系统。我们成功研制了一种低温-高磁场-近场扫描光学显微镜，工作在70 mK。我们研究了二维电子系统和量子点接触在高磁场下的成像。我们得到了宽条带和窄条带的图像，它们可能反映了二维电子系统中光学产生的电子在体态和边缘态的扩散。用磁光致发光法测定了在垂直磁场1.5<r_s<6范围内的电子和空穴有效质量。我们发现得到的有效质量随着电子密度的减小而增大。在量子管中观察到光致发光峰值能量的振荡取决于通过管的磁通量。这些能量的振荡被证明是由于量子管中带电激子的AB效应。我们的研究有助于实现半导体纳米结构中新型相关电子态的外部控制。

One of the great advantages of semiconductor nanostructures is that the electronic states as well as spin states can be designed artificially. This enables us to prepare electronic states in semiconductor nanostructures which manifest novel physical properties. The purpose of this research is to detect novel correlated electronic sates in externally controllable semiconductor nanostructures. We have developed spatially resolved circularly-polarized spectroscopic system at low temperatures and at high magnetic fields. We have successfully developed a low temperature-high magnetic field-near field-scanning optical microscope operated at 70 mK. We have studied imaging of two dimensional electron system and quantum point contacts in high magnetic fields. We have obtained images of broad and narrow strips presumably reflect the diffusion of the optically created electrons in the bulk and the edge states in two dimensional electron system. We have determined of the electron and hole effective masses in perpendicular magnetic fields in the range between 1.5<r_s<6 by magneto-photoluminescence measurements. We find that the obtained effective masses increase with decrease in electron density. The oscillations of the photoluminescence peak energies are observed in quantum tubes depending on the magnetic flux through the tube. These oscillations in energies are shown to be due to the AB effect of a charged exciton in a quantum tube. Our research contributes to realize external control of novel correlated electronic sates in semiconductor nanostructures.