CAREER: Topological order and edge states in fractional quantum Hall systems

George Mason University, Fairfax VA

Investigators

Abstract

Nontechnical Abstract: Future technologies based on quantum materials and devices are expected to have applications with significant practical impact on everyday life and to provide help in solving many of today’s global challenges. This project aims to address some of the important fundamental questions about the complex phases in graphene materials used to make quantum devices. The complex special properties of these materials make them potential building blocks for future quantum computers. Various physical observables which can reflect the topological properties found in these materials are explored, with a particular focus on entropy and the way charges flow. This research helps to provide the critical fundamental knowledge required for the advancement of future topological quantum computing schemes. These new quantum technologies need an educated labor force to properly utilize the breathtaking possibilities. Therefore, the educational plan in this project focuses on creating a new generation of quantum material scientists by promoting outreach and educational opportunities for students and underrepresented groups and enhancing community’s knowledge of quantum nanoscience and nanoelectronics by a mixture of training, designing new courses and seminar series. Technical Abstract: Understanding quantum correlated phases in two dimensional systems is important for both fundamental physics and quantum-based applications. Specifically, the fractional quantum Hall effect (FQHE) is an exemplar of a topological phase of matter which provides a rich platform to study emergent phenomena and quantum statistics. While various techniques have been applied to tackle the issues of statistics and topology in FQH states over the last decade, the critical fundamental knowledge required for applications is still lacking. The topological properties of FQH states can be reflected in the entropy carried by their emergent quasiparticles, the internal structures of their edge channels, and the conductance across their specific interfaces. This project is focused on utilizing less explored approaches to measure these physical observables which can give valuable insights into the underlying topology and statistics of the FQH states. This research relies on the fabrication of clean graphene heterostructures and engineering of gate-tunable interfaces, where topologically distinct FQH phases can be interfaced within a single device. The FQH physics in these systems is investigated by a combination of thermopower, electrical transport and local probe measurements. These studies address some of the most important fundamental questions in this field. For example, what is the thermodynamic entropy carried by emergent quasiparticles of FQH states and how it can be used to distinguish Abelian and non-Abelian states? Can interfacing various FQH states be used to identify the topological order of these states or help to resolve the black hole information paradox? Addressing these questions can have important implications for the development of topological quantum computing schemes and may provide valuable insights into one of the long-standing problems in cosmology. 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.