Topological Frustration Induces Unconventional Magnetism in a Nanographene

Finite-sized graphene molecules comprising identical hexagonal rings in one plane are so-called nanographenes (NGs), which show dependence of the intrinsic electronic structure on the topologies of the edge bonds and the π-electron network. In 1972, Erich Clar envisioned the Clar’s Goblet, a D_2h-symmetric nanographene with a concealed non-Kekulé structure and two unpaired electrons, creating a magnetically non-trivial ground state.

Very recently, researchers from the Technische Universität Dresden (Chair of Molecular Functional Materials) and collaborators (EMPA, Zurich, Switzerland) with expertise in on-surface physics and chemistry reported the first experimental realization of the Clar’s Goblet via combined in-solution and on-surface synthesis. Subsequent low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) reveal an antiferromagnetic intrinsic property with a large exchange coupling of 23 meV when the Clar’s Goblet is adsorbed on the gold surface. Furthermore, switching of the magnetic ground state by atomic manipulation provides direct evidence of carbon magnetism in the simple, bow-tie shaped nanographene.

Reference:
“Topological frustration induces unconventional magnetism in a nanographene”

Shantanu Mishra, Doreen Beyer, Kristjan Eimre, Shawulienu Kezilebieke, Reinhard Berger, Oliver Gröning, Carlo A. Pignedoli, Klaus Müllen, Peter Liljeroth, Pascal Ruffieux, Xinliang Feng, Roman Fasel

Nat. Nanotechnol. 2019, xxx, DOI: 10.1038/s41565-019-0577-9

This work was financially supported by the Swiss National Science Foundation (grant nos 200020-182015 and IZLCZ2-170184), the NCCR MARVEL funded by the Swiss National Science Foundation (grant no. 51NF40-182892), the European Union’s Horizon 2020 research and innovation programme under grant agreement nos 696656 and 785219 (Graphene Flagship Core 2), the Office of Naval Research (N00014-18-1-2708), ERC Consolidator grant (T2DCP, no. 819698), the German Research Foundation (DFG) within the Cluster of Excellence Center for Advancing Electronics Dresden (cfaed) and EnhanceNano (no. 391979941), and the European Social Fund and the Federal State of Saxony (ESF-Project GRAPHD, TU Dresden). We acknowledge computational support from the Swiss Supercomputing Center (CSCS) under project ID s904; S. K. and P. L. acknowledge funding from the Academy of Finland (grant nos 309975 and 318995) and the European Research Council (ERC-AdG no. 788185) and the facilities of the Aalto Nanomicroscopy Centre.