Nontechnical Abstract: Over the past few years, the intensive research effort in layered 2-dimensional (2D) materials has led to an extraordinary discoveries. Of particular interest are phenomena that arise because of the particular geometry, electronic structure and dimensionality of these systems. Moreover, a new degree of freedom, namely the relative twist angle between the crystalline lattices in heterostructures formed from these 2D systems, enables the fabrication of an effectively infinite class of new materials, most of which are waiting to be investigated. The research objective of this project is to explore the quantum electronic properties of these so-called twisted van der Waals heterostructures, with especial emphasis on elucidating how tuning the twist-angle influences their properties, and build upon this understanding to engineer novel quantum devices. We plan to achieve the proposed research objective through the nanofabrication, transport and spectroscopic measurements of one of the simplest, yet most intriguing, vdW heterostructures: that made by stacking two graphene sheets, or twisted bilayer graphene (TwBLG). This research activity is part of a broadly integrated program aimed at building a collaborative and open scientific community, mentoring the next-generation of scientists, and communicating physics to industry leaders and the general public.
Van der Waals heterostructures constitute ideal platforms to explore a variety of new electronic, correlated, and topological phenomena, due to the vast range of layered materials currently available and the extensive freedom in choosing the stacking order and rotational alignments. We plan to investigate quantum spin Hall physics and correlated superconductivity in TwBLG via quantum electronic transport measurements at low temperatures and variable magnetic fields. This research activity advances our knowledge of the effects of interlayer coupling and many-body correlations on the resultant electronic and topological behavior of graphene-based vdW heterostructures, a subject with ramifications in all areas of condensed matter physics. Moreover, this research has impacts well beyond two-dimensional materials and condensed matter physics research: the interplay between interactions, superconductivity, and topology in systems described by the Dirac equation (e.g. in TwBLG) is of keen interest to other physics disciplines, such as the physics of ultra-cold atoms and high energy physics. This research may also result in novel quantum circuits of interest for topologically-protected quantum computing, and is of importance in assessing the potential of vdW materials as key components of future nanoelectronics and quantum information technologies.
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.
