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Topological frustration induces unconventional magnetism in a nanographene

Shantanu Mishra1, Doreen Beyer2, Kristjan Eimre1, Shawulienu Kezilebieke3, Reinhard Berger2, Oliver Gröning1*, Carlo A. Pignedoli1*, Klaus Müllen4, Peter Liljeroth3, Pascal Ruffieux1, Xinliang Feng2, Roman Fasel1,5*

1 nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland

2 Faculty of Chemistry and Food Chemistry, and Center for Advancing Electronics Dresden, Technical University of Dresden, Dresden, Germany

3 Department of Applied Physics, Aalto University, Espoo, Finland

4 Department of Synthetic Chemistry, Max Planck Institute for Polymer Research, Mainz, Germany

5 Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland

* Corresponding authors emails: oliver.groening@empa.ch, carlo.pignedoli@empa.ch, roman.fasel@empa.ch
DOI10.24435/materialscloud:ha-t5 [version v1]

Publication date: Jul 15, 2020

How to cite this record

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, Topological frustration induces unconventional magnetism in a nanographene, Materials Cloud Archive 2020.79 (2020), doi: 10.24435/materialscloud:ha-t5.

Description

The chemical versatility of carbon imparts manifold properties to organic compounds, where magnetism remains one of the most desirable but elusive. Polycyclic aromatic hydrocarbons, also referred to as nanographenes, show a critical dependence of electronic structure on the topologies of the edges and the π-electron network, which makes them model systems with which to engineer unconventional properties including magnetism. In 1972, Erich Clar envisioned a bow-tie-shaped nanographene, C38H18, where topological frustration in the π-electron network renders it impossible to assign a classical Kekulé structure without leaving unpaired electrons, driving the system into a magnetically non-trivial ground state. In this record we include data needed to support our recent work where we demonstrate the experimental realization and in-depth characterization of this emblematic nanographene, known as Clar’s goblet. Scanning tunnelling microscopy and spin excitation spectroscopy of individual molecules on a gold surface reveal a robust antiferromagnetic order with an exchange-coupling strength of 23 meV, exceeding the Landauer limit of minimum energy dissipation at room temperature. Through atomic manipulation, we realize switching of magnetic ground states in molecules with quenched spins. Our results provide direct evidence of carbon magnetism in a hitherto unrealized class of nanographenes, and prove a long-predicted paradigm where topological frustration entails unconventional magnetism, with implications for room-temperature carbon-based spintronics.

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Files and data are licensed under the terms of the following license: Creative Commons Attribution 4.0 International.
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External references

Journal reference
S. Mishra, D. Beyer, K. Eimre, S. Kezilebieke, R. Berger, O. Gröning, C.A. Pignedoli, K. Müllen, P. Liljeroth, P. Ruffieux, X. Feng and R. Fasel, Nat. Nanotechnol. 15, 22-28 (2020) doi:10.1038/s41565-019-0577-9

Keywords

MARVEL/DD3 SNSF ERC Clar goblet Kondo nanographene ab initio

Version history:

2020.79 (version v1) [This version] Jul 15, 2020 DOI10.24435/materialscloud:ha-t5