Career Fair and Career Events

Efthimios Kaxiras

Harvard University

Professor

Faculty Host: Sahar Sharifzadeh

Student Host: Arielle Cohen

Refreshments at 2:45 PM

Localization with a Twist: Electronic States in Incommensurately Stacked 2D Layers

Abstract:

The stacking of individual layers of two-dimensional materials can be experimentally controlled with remarkable precision on the order of a tenth of a degree. The relative orientation of successive layers introduces variations in the electronic properties that can be controlled by the twist angle. We use simple theoretical models and accurate electronic structure calculations to predict that the electronic density in stacked 2D layers can vary in real space in a manner similar to the band-structure in momentum-space, creating moire super-lattices. A direct consequence of the patterns is the localization of electronic states. We demonstrate this effect in graphene, a semi-metal, and MoSe2, a representative material of the transition metal dichalcogenide family of semiconductors. This effect can be useful in the design of localized electronic modes with specific geometries for experimental or technological applications, including superconductivity, as has been recently reported for 2D twisted bilayer graphene.

Bio:

Prof. Efthimios Kaxiras received a PhD in theoretical condensed matter physics from MIT, was a Postdoctoral Fellow at the IBM T.J. Watson Research Center, and joined the faculty of Harvard University in 1991 where he is the John Hasbrouck Van Vleck Professor of Pure and Applied Physics. He is the Founding Director of the Institute for Applied Computational Science, served as the Director of the Initiative on Innovative Computing, and his distinctions include Fellow of the American Physical Society and Chartered Physicist of the Institute of Physics. His research interests encompass a wide range of topics in the physics of solids and fluids, most recently on materials for renewable energy, heterogeneous catalysis on metal surfaces, and the electronic properties of two-dimensional solids like graphene.