Motivated by the InSb nanowire superconductor system, we investigate a systemwhere one-dimensional topological superconductors are placed in parallel. Itwould be simulated well by a ladder of the Kitaev chains. The system undergoesmultiple topological phase transitions, where the number of Majorana fermionschanges as a function of the interchain superconducting pairings. Weanalytically determine the topological phase diagram by explicitly calculatingthe topological number and the band structure. They show even-odd effects withrespect to the number of legs of the ladder. When the relative phase betweenthe inter- and intrachain superconducting pairings is 0 or $\pi$, the systembelongs to the class BDI characterized by the $\mathbb{Z}$ index, and otherwiseit belongs to the class D characterized by the $\mathbb{Z}_2$ index. Thistopological class change would be caused by applying the Josephson current oran external magnetic field, and could be observed by measuring the zero-biasdifferential conductance.
展开▼
