A molecule with half-Möbius topology
Summary
Stereoisomers of C13Cl2 exhibiting helical orbitals around a ring of carbon atoms were synthesized by atom manipulation on NaCl surfaces. We resolved the enantiomeric geometries of the singlet states by atomic force microscopy and mapped their helical orbital densities by scanning tunneling microscopy. A π-orbital basis of the helical, nonplanar 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 wit
Content
# A molecule with half-Möbius topology
*Published: 2026 May 7*
Stereoisomers of C13Cl2 exhibiting helical orbitals around a ring of carbon
atoms were synthesized by atom manipulation on NaCl surfaces. We resolved the
enantiomeric geometries of the singlet states by atomic force microscopy and
mapped their helical orbital densities by scanning tunneling microscopy. A
π-orbital basis of the helical, nonplanar 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. A quasiparticle on a ring with
this boundary condition could be interpreted as carrying a Berry phase of π/2.
We demonstrate reversible switching of the topology between the two singlets of
oppositely threaded half-Möbius topology and the planar, topologically trivial
triplet state. Multireference calculations, including large-scale, sample-based
ab initio calculations executed on quantum hardware, revealed that the switching
is associated with a helical pseudo-Jahn-Teller effect.
DOI: 10.1126/science.aea3321