Experimental Investigation of Delocalization and Phase Diagram in Quantum Hall Systems

9705439 Jiang本实验研究项目主要研究量子霍尔效应下的二维电子气体，特别是受无序影响的相图和局域-离域跃迁。门控GaAs/AlGaAs器件将用于控制实验系统的有效失序。高磁场输运实验将研究磁场诱导的离域跃迁，并确定无序磁场平面上的相图。边态隧道光谱将用于探测各种电子相的微观性质和低能激发。本实验研究项目致力于研究二维平面区域内导电电子系统的基本性质。在低温和强磁场下，这样一组受限的电子表现出一组非常不寻常的特征，这对那些希望测试和扩展晶体固体中电子基本理论的理论家来说是很有兴趣的。改进后的理论可以更有信心地应用于微电子和其他技术中重要的金属和半导体。这个项目的实验集中在已经观察到的“金属-绝缘体”跃迁上，特别是它是如何与电子环境中的无序相关联的。一方面，这些实验将提供关于电子在低温条件下在受限层中相互作用的新的基本信息。另一方面，这些实验中使用的器件结构与气体技术中使用的先进微电子器件相似。这项研究将涉及在物理领域受过良好训练的学生，他们将熟悉半导体器件技术，并将为工业，政府或教育部门的就业提供出色的培训。＊＊＊

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. ***