Fig. 3: The point-mass adsorbed Su-Schrieffer-Heeger (aSSH) model at equilibrium, polyyne–like equivalent under thermal fluctuations and their bulk-boundary correspondence.
a The aSSH model is realised by a four-parameter dynamical matrix: Mass mC, mM and bonds κ1, κ2; and interaction with a virtual semi-unmovable substrate (blue line on the blue surface) via κ3. This point-mass model overall mimics the molecular mechanics parameters of polyyne strongly adsorbed on a substrate (but without vdW parameters, angles nor dihedrals). Two masses per unit cell are allowed to move either parallel or perpendicular to the substrate. Here, the case of the transversal (T) mode crossing the lower energy mode (LA) is depicted in yellow. b Band dispersion from molecular dynamics simulations of an infinite-chain of 52 masses at finite temperature. Power spectral density (PSD) of the periodic chain shows a spectrum comparable to the point-mass mode. The influence of the T mode leads to a change in the LA band, see Supplementary Fig. 9. c, d A finite-chain with localised heavy-boundary masses expresses a longitudinal topological boundary mode (magenta arrow in c), whose eigenmode is depicted transversally in d for convenience. Source data are provided as a Source Data file.
