Delocalization and Phase-transition in Quantum Hall Devices

在低温和强磁场条件下对GaAs/AlGaAs二维电子气体进行输运实验。提出的实验包括研究安德森绝缘体在磁场中的输运性质，研究绝缘体与量子霍尔液体之间相变的临界指数，以及研究磁场无序平面上量子霍尔效应的全局相图。跃迁的离域过程和一般标度特性可能对理解其他低维量子系统很重要。在人工分层的半导体中可以制造出非常薄的电子片。这种电子二维（2D）导体具有重要的器件潜力，但也可以作为测试最新理论预测的理想系统。栅极能使电子气体的性质从导体的性质转变为绝缘体的性质。外加磁场可使绝缘相变为导电相。提出了在低温下研究二维电子气与外加偏置和磁场的关系。这些结果将与最近发表的一项综合理论进行比较。该结果有望对其他低维电子系统的理解产生影响。＊＊＊

9313786 Jiang Transport experiments will be carried out on the GaAs/AlGaAs two- dimensional electron gas in the quantum Hall regime at low temperatures and high magnetic fields. The proposed experiments include study of the transport properties of the Anderson insulator in a magnetic field, investigation of the critical exponents of the phase transition between the insulator and the quantum Hall liquid, and study of the global phase diagram of the quantum Hall effect in the magnetic field-disorder plane. The delocalization processes and general scaling properties of the transitions are likely to be important to the understanding of other low dimensional quantum systems. %%% Very thin sheets of electrons can be created in artificially layered semiconductors. Such electronic two dimensional (2D) conductors have significant device potential but can also serve as ideal systems for testing recent theoretical predictions. A gate electrode can alter the character of the electron gas from that of a conductor to an insulator. An applied magnetic field can revert an insulating phase to a conducting phase. It is proposed to study the 2D electron gas as a function of applied bias and as a function of magnetic field at low cryogenic temperatures. The results will be compared to a recently published comprehensive theory. The results are expected to have an impact on the understanding of other low dimensional electronic systems. ***