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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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In this talk, I will revisit a few old issues in the quantum Hall effect in high quality two-dimensional electron systems (2DES). Of the first example, I will present our experimental results to quantitatively examine the theoretical model of spin splitting collapse in the quantum Hall regime at fixed magnetic fields as a function of electron density in a high quality heterojunction insulated-gate field effect transistor. In the second part, I will talk about the quantum criticality of quantum Hall (QH) plateau to plateau transitions in alloy disordered two-dimensional electron systems. The QH plateaus represent separate energy regions of localized states, while between two adjacent plateaus there is a critical field Bc associated with one energy level of extended states. The plateau-to-plateau transition is therefore an Anderson localization-delocalization transition. Our recent work focusing on alloy disorder in AlxGa1-xAs/Al0.32Ga0.68As heterostructure has brought new insight on this problem. Our result manifests unequivocally that in an Anderson disordered 2DES the scaling behavior indeed prevails. Moreover, our temperature and size dependent data allow direct determination of both the localization critical exponent, n = 2.38, and the dynamical exponent, z = 1. Time permitted, I will also discuss the resistivity law observed about 30 years ago in high quality 2DES.
