Alexandre Artaud

Competing structural phases in graphene on Re(0001)

Phase transition is a transverse physical concept which has provided a framework for various phenomena, from the spontaneous symmetry breaking in particle physics to the evolution of macroeconomic systems. In this context, graphene supported by a substrate like Re(0001) offers a platform where a large diversity of phases can be formed in competition.

First, I will present the structure of the graphene-Re(0001) system observed by Scanning Tunneling Microscopy (STM), where in principle an infinity of quasi-degenerate commensurate phases can be formed. Experimentally, many of such structural phases chaotically coexist at the atomic scale. The precise determination and classification of such phases will be addressed. Still, this coexistence raises the issue of the graphene-Re(0001) ground state, and whether it can be reached.

Insight can be found about this by considering the competition between kinetics and thermodynamics in the formation of graphene. I will then expose this interplay, and how it leads to a growth scenario that goes along multiple paths in parallel. This complex scenario not only accounts for the diversity of observed phases, but explains the structure of so far overlooked graphene defects at the atomic scale.