Quantum electron solids and interaction-driven phenomena in two- and one-dimensional systems

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Nontechnical: Electrons are tiny quantum mechanical objects that exist in all physical systems and most systems contain a large number of them. Understanding how electrons interact with each other and with the environment is a vital scientific subject and has played a critical role in advancing modern science and technologies. Analogous to water, electrons manifest both gaseous states at high temperatures and liquid states at low temperatures. Another form is a solid state which was predicted but never observed. To obtain evidence of this solid state of electrons is not only important in understanding how the most basic force can radically affect the quantum states, but also allows scientists to develop remarkable future quantum electronics and spintronics. These energy sustainable systems are fundamentally important to nature. With greatly improved semiconductor technologies, a novel type of semiconductors of ultra-high purity has become available as a result of a recent breakthrough and preliminary results have been recently obtained as evidence of a genuine quantum electron solid. This project utilizes such devices to perform experiments with the most advanced scientific tools: nanofabrication and ultra-low temperature physics. The goal is to capture the direct evidence for the quantum mechanical mechanisms in the dynamical properties. This project supports the education of one Ph.D. student in pursuing discovery and advanced technologies, and allows the group to conduct outreach activities with local high schools. Technical: Remarkable new quantum phenomena, such as the even-denominator Fractional Quantum Hall Effect and Topological Insulators, emerge in response to strong inter-particle Coulomb interaction. However, the most prominent interaction-driven effect, Wigner crystallization of electrons, has not been well established. This fascinating quantum matter (with spin ordering) is not only paramount to fundamental science, but also important for future applications including quantum electronics and spintronics. For a long time, experimental effort was hindered because most devices contain a high level of unwanted disorder which overwhelms the interaction effect at low electron densities. Since 2003, breakthroughs have been made in providing ultra-high quality two-dimensional electron systems in GaAs semiconductor field-effect-transistors. Recent achievement with the measurement of ultrahigh purity GaAs field-effect transistors (named HIGFET) has led to the observation of a genuine WC. Moreover, the preliminary results also point to possible quantum pinning/depinning mechanisms that are not understood. This project utilizes these types of devices with record low electron densities to perform transport experiments at mK temperatures. The goal is to verify the quantum nature of the dynamical properties well below the classical limits. Various techniques such varying temperature, density, and interaction are adopted to study the phase boundaries. AC+DC excitation technique is utilized to directly probe the collective, large-scale quantum tunneling in a Wigner Crystal. This project supports the education of one Ph.D. student in pursuing discovery and in learning advanced technologies, which are indispensable for excellent training in pursuing scientific careers.