Abstract | Higher-order topological superconductors are characterized by Majorana modes localized at corners or hinges. Topological phase transitions in these higher-order phases can be driven by variations in a bulk parameter without closing the bulk gap. This presents a challenge in establishing a direct bulk-boundary correspondence, as conventional bulk invariants change only upon the closure of the bulk gap. In this talk, I will introduce our recent studies of two-dimensional higher-order topological superconductors in D, DIII and BDI symmetry classes. We demonstrate that in certain phases, a pair of topological invariants that are derived from Fermi level crossings can be used to characterize higher-order topology. These invariants may change with the closure of either bulk or edge gaps, thereby providing a clear demonstration of bulk-boundary correspondence in these higher-order phases. References： [1] Hong Wang and Xiaoyu Zhu, PRB 108, 125426 (2023). [2] Xiaoyu Zhu, arXiv:2403.17635 (2024). |
