Electron-Electron Interaction Driven Phase Transition in Low Dimensional Systems

Wayne State University, Detroit MI

Investigators

Abstract

****Technical Abstract**** The study of the many-body electron systems encompasses two of the most fundamental subjects: electron-electron interaction and electron-disorder interaction. It is well known that sufficient disorder causes electron states to undergo Anderson Transition. On the other hand, whether strong electron-electron interaction also brings radical changes, such as the predicted Wigner Crystallization (electron solid), is still unknown. 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. Recent breakthroughs have been made in providing ultra-high quality two-dimensional electron systems in GaAs semiconductor field-effect-transistors. This project will utilize this type of devices with record low electron densities to perform transport experiments at low temperatures. The goal is to verify whether strong electron-electron interaction drives a first-order phase transition (Wigner crystallization) or some intermediate phases. Either observation will provide insights in understanding the quantum mechanical nature of strongly interacting electrons in the form of a solid or a strongly correlated liquid. This project will support the education of one Ph.D. student in pursuing discovery and in learning most advanced technologies, which has historically shown to be excellent training for scientific careers. ****Non-Technical Abstract**** Electrons are quantum mechanical objects that exist in all physical systems and most systems contain a large number of them. Understanding the states of electrons, how they interact with the environment and each other, 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 of the states is solid which was predicted but never observed. To obtain evidence of this solid state of electrons is not only important to understand how the most basic force among the electrons can radically affect the quantum states, but also allow scientists to utilize remarkable properties in developing quantum electronics and spintronics. As nanotechnology marks the opening of the 21st century, semiconductor technologies have greatly improved. A novel type of semiconductors of ultra-high purity has become available as a result of a recent breakthrough. This project will utilize such devices to perform experiments with the most advanced scientific tools: nanofabrication and ultra-low temperature physics. The goal is to capture direct evidences that either indicate an electron solid, or some other complex states. This project will support the education of one Ph.D. student in pursuing discovery and in learning most advanced technologies, and allow the group to conduct outreach activities with local high schools.