Fig. 2: Mass dimer.
From: Strain topological metamaterials and revealing hidden topology in higher-order coordinates
a The chiral symmetry of mass dimer—revealed on strain coordinates—leads to a well-defined winding number. Nonzero winding makes the configurations with P < 1 topologically non-trivial. b Evolution of the spectrum of a finite chain with an odd number of particles (21) and free boundaries as we change the parameter P. Edge states emerge for P < 1. Colormap confirms localization of states inside the band gap. c Spectrum of a finite chain in displacement and strain coordinates at P = 0.25. Except for the zero mode, the spectrum is the same in both coordinates and shows chiral symmetry about the mid-gap frequency ω2 = 1. d Profiles of the edge states in c. Their chiral nature is revealed in strain coordinates.
