Twofold topological phase transitions induced by third-nearest-neighbor hoppings in one-dimensional chains

Strong long-range hoppings up to third-nearest neighbors may induce a topological phase transition in one-dimensional chains. Unlike the Su-Schrieffer-Heeger model, this transition from trivial to topological phase occurs with the emergence of a pseudospin valley structure and a twofold nontrivial topological phase. Within a tight-binding approach, these topological phases are analyzed in detail and it is shown that the low-energy excitations follow a modified Dirac equation, in which the dynamics of particles with positive and negative mass occur differently. An experimental realization in a one-dimensional elastic chain, where it is feasible to tune directly the third-nearest-neighbor hoppings, is proposed.