Experiments on the Role of Disorder in the Quantum Phases and Phase Transitions of Two-Dimensional Electrons

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Technical:The two-dimensional electron systems (2DES) in semiconductor heterostructures has been a hot bed for new physical phenomena, manifesting strong correlation physics, and a testing ground for novel theoretical ideas. Physics research on the system has in the past mostly focused on the correlation physics of ideally clean systems and the experiments have been designed and carried out on 2DES with the highest mobility attainable at the time. This research will focus on three new material/device structures to access previously inaccessible physical regimes of dilute 2DES with controllably tunably disorder. DC transport and microwave spectroscopy measurements will be made at low T down to the nuclear demagnetization refrigerator temperature range to search for the expected new phases of electron matter intermediate to the Wigner crystal in clean 2DES and the Anderson insulator in highly disordered 2DES. It will educate students in condensed-matter physics and the science of semiconductor materials. They will be equipped with hands-on expertize in experimental low temperature physics techniques and semiconductor device processing technology. Non-Technical:In modern day electronics, almost all device functions are performed by electrons that are confined to move in thin films, or along the interfaces, of semiconductors. Such so-called two-dimensional electrons in semiconductors, though behaving at normal ambient as an ordinary gas of charged particles, have been under properly designed experimental conditions a hot bed for new physical phenomena, manifesting the quantum physics of strongly correlated electrons, and a testing ground for novel theoretical ideas. This research will investigate the influence of disorder, which is inevitable in all semiconductors, and explore a new physical regime, where the interplay between disorder and electron correlation is expected to give rise to new phases of the electron matter. The research is multidisciplinary in nature; it will educate students to be fluent in condensed-matter physics and the science of semiconductor materials, and equip them with hands-on expertize in experimental low temperature physics techniques and the processing technology of semiconductor devices.