Kavli Affiliate: Michael F. Crommie
| First 5 Authors: Ziyi Wang, Ziyi Wang, , ,
| Summary:
Structurally distorting low-dimensional pi-conjugated systems can
profoundly influence their electronic properties, but controlling such behavior
in extended-width systems remains challenging. Here we demonstrate that a
one-dimensional conjugated polymer, poly-(difluorenoheptalene-ethynylene)
(PDFHE), undergoes a pronounced out-of-plane backbone distortion, equivalent to
a spontaneous symmetry breaking (SSB) of its mirror symmetry. We synthesized
PDFHE on noble metal surfaces and characterized its structure and electronic
states using low-temperature scanning tunneling microscopy. Rather than
adopting a planar, high-symmetry conformation, PDFHE relaxes into non-planar
isomers stabilized by a Jahn-Teller-like mechanism that relieves an electronic
instability relative to the gapped planar structure. Density functional theory
calculations corroborate these findings, revealing that distortion lowers the
total polymer energy and enlarges the bandgap, providing a microscopic
explanation for the SSB. Our results show that even in mechanically robust
extended pi-systems, subtle electron-lattice coupling can spontaneously
drive significant structural rearrangements.
| Search Query: ArXiv Query: search_query=au:”Michael F. Crommie”&id_list=&start=0&max_results=3