Condensed Matter Seminar: "Atomic Crystals with New Twists"

Wed, 03/29/2017 - 16:00 - 17:00
Jiwoong Park, Cornell University

Chiral materials possess left- and right-handed counterparts linked by mirror symmetry, with applications in physics, chemistry and biology. In atomic crystals such as graphene, chiral symmetry emerges naturally as a consequence of the honeycomb lattice. In this talk, I will discuss two recent studies where the interaction between graphene and another surface breaks this chiral symmetry. The first example is chiral twisted bilayer graphene, a two-atom-thick chiral film, with giant circular dicrhoism. It is produced using a chiral stacking approach, where two graphene layers are positioned layer-by-layer with precise control of the interlayer rotation and polarity, resulting in tunable chiral properties of the final stack. The second example is the formation of KekulĂ© bond order, a phase of broken chiral symmetry, in an ultraflat graphene sheet grown epitaxially on a copper substrate. Its origin lies in the interactions between individual vacancies in the copper substrate that are mediated electronically by the graphene.

David Rittenhouse Laboratory, A4