Breaking Peierls theorem in polyacetylene chains via topological design

Abstract

Peierls theorem postulates that a one-dimensional (1D) metallic chain must undergo a metal-to-insulator transition via lattice distortion, resulting in bond length alternation (BLA) within the chain. The validity of this theorem has been repeatedly proven in practice, as evidenced by the absence of a metallic phase in low-dimensional atomic lattices and electronic crystals, including conjugated polymers, artificial 1D quantum nanowires, and anisotropic inorganic crystals. Overcoming this transition enables realizing long-sought organic quantum phases of matter, including 1D synthetic organic metals and even high-temperature organic superconductors. Herein, we demonstrate that the Peierls transition can be globally suppressed by employing lattice topology engineering of classic trans-polyacetylene chains connected to open-shell nanographene terminals. The appropriate topology connection enables an effective interplay between the zero-energy modes (ZMs) of terminal and the finite odd-membered polyacetylene (OPA) chains. This creates a critical topology-defined highest occupied molecular orbital (HOMO) that compensates for bond density variations, thereby suppressing BLA and reestablishing their quasi-1D metallic character. Moreover, it also causes the formation of an unconventional boundary-free resonance state, being delocalized over the entire chain with non-decaying spectral weight, distinguishing them from traditional solitons observed in polyacetylene. Our finding sets the stage for pioneering the suppression of material instability and the creation of synthetic organic quantum materials with unconventional quantum phases previously prohibited by the Peierls transition.