Prof. Ellad B. Tadmor
Aerospace Engineering and Mechanics Department
University of Minnesota

Moiré Mechanics in 2D Materials

ABSTRACT: The synthesis of graphene, a one-atom thick two-dimensional (2D) graphitic sheet, was a revolution in materials physics. Since then, a host of other 2D materials have been discovered that can be stacked and manipulated to create layered heterostructures with remarkable properties (including the recent discovery of superconductivity in twisted graphene bilayers). Such properties are related to structural reconstructions that occur in 2D heterostructures starting from an initial moiré pattern that is created when mismatched layers are stacked. Taking graphene bilayers as an example, I will describe the mechanics and physics of these fascinating materials and show how they can be modeled using a combination of nonlinear continuum finite elements and high-fidelity machine learning interatomic potentials. These simulations predict an interesting scaling behavior in the reconstruction that is related to the initial imposed twist and leads to qualitative change in electron diffraction patterns, which was subsequently verified experimentally.

BIOGRAPHY: Ellad Tadmor is a Professor of Aerospace Engineering and Mechanics at the University of Minnesota. He received his B.Sc. and M.Sc. in Mechanical Engineering from the Technion - Israel Institute of Technology in 1987 and 1991, and his Ph.D. from Brown University (USA) in 1996. He pioneered computer simulation methods and theories that span multiple length and time scales to predict the behavior of materials and nanodevices, including 2D materials, from their atomic structure. He has published over 70 papers in this area and two graduate-level textbooks. Professor Tadmor is the Founding Director of the NSF Open Knowledgebase of Interatomic Models (OpenKIM), which is a web-based cyberinfrastructure tasked with developing standards and improving the reliability of atomistic simulations, and is on the Editorial Board of the Journal of Elasticity.