Presenter: Prof.Roman Fasel (Swiss Federal Laboratories for Materials Science and Technology)
Topic: Polybenzenoid hydrocarbons with intrinsic π-magnetism
Time: 10:00 AM, June. 27th (Thursday)
Location: Conference Room B, BLDG 909-1F
Topologies of the edge bonds and π-electron network critically influence the electronic structure of polybenzenoid hydrocarbons, and may lead to properties that are otherwise absent in the parent material graphene. Among various properties that arise in hydrocarbon compounds due to the chemical versatility of carbon, intrinsic magnetism remains one of the most desirable but also elusive.
In this presentation, I will discuss the on-surface synthesis and scanning tunneling microscopy / spectroscopy-based characterization of polybenzenoid hydrocarbons with peculiar structural topologies entailing intrinsic π-magnetism on metal surfaces. In particular, I will present the first experimental realization of Clar’s goblet, an elusive non-Kekulé compound that has been predicted since decades. Magnetism in Clar’s goblet arises due to complete topological frustration of the π-electron network, and the predicted antiferromagnetic ground state is confirmed through inelastic spin excitation spectroscopy. Furthermore, I will discuss recent progress towards synthesis of polybenzenoid hydrocarbons with complete zigzag edge topology, which represents a distinct route towards inducing magnetism in carbon-based nanomaterials. Finally, presence of unpaired spin renders these structures susceptible to spin quenching, and the controllable switching of magnetic ground state through atomic manipulation will be demonstrated.
 O.V. Yazyev, Rep. Prog. Phys. 73, 056501 (2010).
 E. Clar, The Aromatic Sextet; Wiley: New York (1972).
Contact: Prof. Lifeng Chi