Probing Exotic Phases of Ultra High Quality Two Dimensional Carrier Systems

Non-technical Abstract: A major research area in solid-state science and engineering is the study of how the electrons in a solid interact. The interaction stems from the repulsion between electrons because of their electric charge, as well as their spin and other degrees of freedom. It leads to exotic, often unexpected, phases of matter. To study these phases and phenomena, it is important to minimize the imperfections, such as impurities and defects, so that electron-electron interaction is the dominating factor. The goal of this project is to experimentally explore and understand the new phases that arise in electron systems with the least amount of imperfections. The project impacts the scientific community and beyond. Results of the research are communicated through publications and conference presentations to the specialized as well as general science and engineering communities. While the subject of this project is fundamental, progress in this area benefits society in the long term as it may lead to novel, transformative concepts for electronic devices and information processing systems, such as a quantum computer, whose operation relies on quantum and/or interaction phenomena. The project also incorporates a high quality and comprehensive educational component as it includes the education of students in critical, state-of-the art areas of science and technology, including the fabrication, characterization, and physics of very high-quality, thin-film semiconductor structures. Well-trained students in these fields are invaluable resources for the US as well as for the rest of the world. Technical Abstract: This project incorporates experimental investigations of electron interaction physics in quantum-confined semiconductor structures with ultra-high quality, as quantified by their world-record mobilities. The focus is on engineering and probing the topological order of various exotic, many-body phases of two-dimensional electron and hole systems confined to selectively-doped GaAs quantum wells fabricated via molecular beam epitaxy. Of particular interest are new even-denominator fractional quantum Hall states that emerge in ultra-high-quality samples. These include the fractional quantum Hall state at Landau level filling factor ½ in wide quantum wells. Very recent experimental data strongly suggest that this state is non-Abelian and yet is surprisingly robust as it has an energy gap of about 6 K, the largest gap reported for any potentially non-Abelian state. This makes the ½ state a prime candidate for a topological quantum computing platform. Also of interest are ultra-high-quality systems of two-dimensional holes which possess a large effective mass and a complex and non-linear Landau level fan diagram. These systems, too, exhibit new even-denominator states some of which are also expected to be non-Abelian and have potential use in topological quantum computing. A main goal of the project is to optimize sample parameters to enhance the robustness of the even-denominator states, to determine their topological order through the identification of their daughter states, and to assess their quasi-particle charge and statistics. Other exotic phases of interacting two-dimensional carrier systems, such as Wigner crystal and stripe/nematic phases, as well as multilayer fractional quantum Hall states, are also investigated. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2611783 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Mansour Shayegan | Institution: Princeton University, PRINCETON, NJ | Award Amount: $687,997 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2611783 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2611783.html