Cloning the Dirac cones of bilayer graphene to the zone center by selenium adsorption

Meng-Kai Lin^1*, Jun Zhao², Joseph A. Hlevyack³, T.-C. Chiang³

¹Physics, National Central University, Taoyuan, Taiwan
²New Energy Technology Engineering Laboratory of Jiangsu Province & School of Science, Nanjing University of Posts and Telecommunications, Nanjing, China
³Physics, University of Illinois at Urbana Champaign, Illinois, USA

* Presenter:Meng-Kai Lin, email:mklin_ncu@outlook.com

Controlled manipulation of Dirac fermions in nontrivial systems is central to the engineering of high performance devices with unusual but versatile transport properties. Surprisingly, through angle resolved photoemission, we demonstrate that such band tuning can even occur through van der Waals molecular adsorption of selenium (Se) vapor onto bilayer graphene terminated SiC surfaces maintained at sufficiently low temperatures. Although elemental Se—a component material in many topological insulators—itself should be topological in certain structural forms, pure Se structures with nontrivial order are energetically unfavorable, and elemental topological systems themselves are quite rare. Here instead, an adsorbed Se layer on bilayer graphene, which is an ordered array of large Se8 molecules based upon our first principles analysis, acts as a natural conduit for generating an emergent clone of graphene’s Dirac cones at the zone center. Overall, our systematic experimental and first principles study not only reveals an underlying cloning mechanism based upon band folding but also offers a new, simple methodology for creating and/or manipulating Dirac fermions via gentle surface modification.

Keywords: angle resolved photoemission spectroscopy, van der Waals materials, molecular adsorption