Fig. 5: An atomistic double-chain adsorbed Su-Schrieffer-Heeger (daSSH) model under thermal fluctuations.

a One nitrogen atom (blue sphere in 3D model) of a DABCO-3Bu molecule coordinates with the iron (purple sphere) of an octaethylporphyrin to form a supramolecular complex. b A double chain of the supramolecular complex is found equivalent to an alternating chain of strong and weak springs resembling the daSSH model. c Eigenmode mapping at 29.3 cm⁻¹ showing eigendisplacements exponentially localised at the second-to-last molecule from the heavy boundary of the finite chain. The colormap represents the angle of the eigenvector’s components with respect to the xy-plane. d–f Band dispersions from molecular dynamics simulations at 10 K identify a (topological) boundary mode as a mid-gap signal. d The case with periodic boundary conditions (PBC) shows a gap between 28 and 32 cm⁻¹ in the power spectral density (PSD). Here, the shaded molecules depict the repetition of the main cell, represented by highlighted molecules. e Creating a boundary by lifting PBC (absent shaded molecules in d) and subsequently f a heavy boundary (heavier molecules marked in red), promotes the appearance of a signal assigned to a daSSH topological boundary mode at 30 cm⁻¹ (marked by a magenta arrow). Source data are provided as a Source Data file.