Fig. 8: Guided excitation of an in-gap free boundary mode.

a, b Band dispersion for molecular dynamics (MD) simulations at 10 K shows a gap between dispersive bulk nodes in the crystal material (a) and a localised boundary mode within this gap for the case of the Ribbon (b). c Eigenmode mapping at 26.7 cm⁻¹ localised at the edges of the Ribbon. The colormap represents the angle of the eigenvector’s components with respect to the xy-plane. d All non-hydrogen atoms of the circled and coloured in red molecule are excited by an oscillating force (period of 1.249 ps or 45.5 cm⁻¹ and force constant 123.4 pN), in the direction corresponding to the eigenmode’s single molecule element in c during MD simulations at 1 K. e The root mean square deviation (RMSD) from the initial minimised configuration for each molecule (with colours corresponding to those in panel d) reveals that the excitation does not propagate to the boundary neighbours. Each RMSD data set is offset by 0.25 Å relative to its (second) nearest neighbour along the (boundary) bulk for clarity. Same-seed trajectories without excitation are provided in the Supplementary Information Fig. 16. Arrows in panel d serve as a guide to the eye for the RMSD fluctuations in e. Source data are provided as a Source Data file.