Postdoctoral Fellowship: MPS-Ascend: Moire Engineering in van der Waals Heterostructures

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Non-technical DescriptionSemiconductors made from a single atomic layer profoundly differ from bulk crystals. For example, two-dimensional (2D) materials combine high mechanical strength and an assortment of tunable electrical properties. One can also make heterostructures with unique functionality by stacking different crystals together. A promising way to control material properties is to vary the relative orientation of two atomically thin layers to create a nanoscale moiré pattern. Such moiré structures have the potential to enable new classes of devices for energy efficient computing and other applications. Currently, the only way to make and control moiré interference patterns is by physically stacking and rotating individual layers. This project will explore the control of moiré lattices by applying mechanical force (strain). Strain engineering is compatible with any type of 2D heterostructure, and thus could enable a wide range of novel devices. Given the enormous amount of energy required for artificial intelligence and data centers, this work could impact everyday technology across the globe. The PI will amplify impact of this work through by mentoring undergraduate students and involving them in research. She will also involve local high school students with hands on experimental work, inspiring a new generation of scientists and engineers.Technical DescriptionThe goal of this MPS-Ascend research project is to obtain a comprehensive understanding of correlated electronic states available in twisted bilayer graphene with respect to both heterostrain (magnitude and direction) and twist angle biases. This systematic study will provide the community a template on how to reliably access and control correlated electron phenomena such as superconductivity in twisted bilayer graphene heterostructures. In addition, we will investigate how to create and control moiré interference patterns in heterostrained non-twisted bilayer graphene structures, then again systematically examine correlated electronic properties with respect to heterostrain application alone. Upon successfully obtaining a moiré interference through heterostrained non-twisted bilayers, this will allow moiré heterostructures to be obtained in a scalable, controllable fashion that can be integrated with industrial nanofabrication processes. As this method is scalable and compatible with any van der Waals based heterostructure, the work can be extended to control more properties dictated by moiré interference patterns and enable device structures that leverage the exotic properties hosted by moiré superlattices.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.