Delocalization and Phase-transition in Quantum Hall Devices

9313786江输运实验将在低温和高磁场下对量子霍尔区的GaAs/AlGaAs二维电子气进行。 这些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-无序平面中量子霍尔效应的全局相图。 跃迁的离域过程和一般标度性质对于理解其他低维量子系统可能是重要的。 在人工分层的半导体中可以产生非常薄的电子片。 这种电子二维（2D）导体具有显著的器件潜力，但也可以作为测试最近的理论预测的理想系统。 栅电极可以将电子气的性质从导体改变为绝缘体。 施加的磁场可以使绝缘相恢复到导电相。 建议在低温下研究二维电子气作为外加偏压的函数和作为磁场的函数。 结果将与最近发表的综合理论进行比较。 这些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. ***