Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 9: Organic molecules on inorganic substrates: electronic, optical and other properties I
O 9.12: Talk
Monday, March 9, 2026, 17:45–18:00, HSZ/0201
A Molecule with Half-Möbius Topology — Igor Roncevic1,2, Fabian Paschke3, Yueze Gao2, Leonard-Alexander Lieske3, Lene A. Gödde2, Jascha Repp4, Florian Albrecht3, Harry L. Anderson2, and •Leo Gross3 — 1Department of Chemistry, The University of Manchester, Oxford Road, Manchester, United Kingdom — 2Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, United Kingdom — 3IBM Research Europe - Zurich, Rüschlikon, Switzerland — 4Institute of Experimental and Applied Physics and Halle-Berlin-Regensburg Cluster of Excellence CCE, University of Regensburg, Regensburg, Germany
Stereoisomers of C13Cl2 exhibiting helical orbitals around a ring of carbon atoms were synthesized by atom manipulation on bilayer NaCl on Au(111). We resolved the enantiomeric geometries of the closed-shell singlet states by atomic force microscopy and mapped their helical orbital densities by scanning tunnelling microscopy. A π-orbital basis of the helical, non-planar singlets that twists by 90∘ in one circulation is consistent with a half-Möbius topology. In such a topology, the π-orbital basis changes sign with respect to two circumnavigations and is periodic with respect to four circumnavigations. This is in contrast to a topologically trivial Hückel basis, which shows no twist, and a Möbius basis, which twist by 180∘ in one circulation. We demonstrate reversible switching of the topology, between the two singlets of oppositely threaded half-Möbius topology, and the planar, topologically trivial, triplet state.
Keywords: tip-induced chemistry; on-surface chemistry; atom manipulation; AFM; STM