First-order topological phase transitions and disorder-induced Majorana modes in extended Kitaev chain*

Using a combination of the mean-field Bogoliubov–de Gennes approach and the density matrix renormalization group method, we discover a first-order topological transition between topological superconducting and trivial insulating phases in a sawtooth lattice of intersite attractive fermions. The topological characterization of different phases is achieved in terms of winding numbers, Majorana edge modes, and entanglement spectra. By studying the effect of disorder on first-order topological phase transitions, we establish disorder-induced topological phase coexistence as a mechanism for generating a finite density of Majorana particles.