The Su-Schrieffer-Heeger (SSH) model alternates weak (v) and strong (w) hoppings. When w>v, the chain is topologically non-trivial (winding number=1), hosting zero-energy edge states protected by chiral symmetry. Thouless pumping cycles the gap.
Topological phase: w/v > 1 → winding number W=1 (edge states exist)
H(k) = (v + w·e^{ik})σ₊ + h.c. | Wind. no. = (1/2πi)∮ d/dk ln det h(k) dk