SSH Chain — Topological Edge States

SSH (Su-Schrieffer-Heeger) model: a 1D chain of dimers with alternating couplings v (intra-cell) and w (inter-cell). For w>v: topological phase with winding number W=1 and Zak phase=π → protected zero-energy edge states localized at chain ends (shown in yellow). For v>w: trivial phase, W=0, no edge states. Disorder cannot remove edge states in the topological phase — topological protection. This is the simplest model for a topological insulator.