Experimental Investigation of Delocalization and Phase Diagram in Quantum Hall Systems

9705439江这个实验研究项目主要集中在量子霍尔效应区的二维电子气，特别是相图和无序对定域-离域相变的影响。实验系统的有效无序将由门控的GaAs/AlGaAs器件来控制。强磁场输运实验将用于研究磁场诱导的离域转变，并确定无序-磁场平面内的相图。边缘态隧道光谱将被用来探测各种电子相的微观性质和低能激发。这个实验研究项目致力于研究导电电子系统在二维平面区域中的基本性质。在低温和强磁场下，这样一组受限的电子显示出一组非常不寻常的特征，这是希望测试和推广晶体固体中电子的基本理论的理论家感兴趣的。因此，改进后的理论可以更有把握地应用于在微电子和其他技术中具有重要意义的各种金属和半导体。这个项目中的实验集中在观察到的一种“金属绝缘体”过渡期，特别是它是如何与电子环境中的无序有关的。一方面，这些实验将提供有关电子在低温下在受限层中相互作用时的新的基本信息。另一方面，这些实验中使用的器件结构与气体技术中的先进微电子器件中使用的器件结构相似。这项研究将包括那些在物理领域受过良好培训并熟悉半导体器件技术的学生，以及那些接受过在工业、政府或教育领域就业的优秀培训的学生。***

9705439 Jiang This experimental research project focuses on the 2-D electron gas in the quantum Hall effect regime, specifically on the phase diagram and a localization-delocalization transition as afffected by disorder . Gated GaAs/AlGaAs devices will be used to gain control of the effective disorder of the experimental system. High magnetic field transport experiments will be carried out to study the magnetic-field-induced delocalization transition and to determine the phase diagram in the disorder-magnetic field plane. Edge-state tunneling spectroscopy will be used to probe microscopic properties and low-energy excitation of various electronic phases. %%% This experimental research project is devoted to basic properties of a conducting electron system when confined in a two-dimensional planar region. Such a confined set of electrons at low temperatures and with high magnetic fields exhibits a very unusual set of characteritics, which are of interest to theorists who wish to test and extend the basic thoery of electrons in crystalline solids. An improved theory then can be applied with more confidence to the wide range of metals and semiconductors which are of importance in microelectronics and other technologies. The experiments in this project are focusing on a "metal-insulator" transiton which ahs been observed and in particular on how it appears in connection with disorder in the environment of the electrons. On the one hand the experiments will provide new basic information about electrons when they are in interaction in confined layers at low temperatures. On the other hand the device structures which are used in these experiments are similar to those used in advanced microelectronic devices in the Gas technology. This research will involve students who will be well trained in the area of physics and will also gain familarity w ith semiconductor device technology, nd who will be excellently trained for employment in industry, government, or education. ***