Rotational symmetry breaking and partial Majorana corner states in a heterostructure based on high- Tc superconductors

Previously, based on a phenomenological model, it was proposed that the higher-order topological superconductivity can be realized in a heterostructure with a two-dimensional topological insulator and a high-temperature superconductor. The Majorana bound states naturally emerge at the corners of the system. Here starting from a microscopic model, we restudy this system theoretically. The symmetries of the quasiparticle energy spectra are significantly different from those previously obtained. In the momentum space, the fourfold rotational symmetry of the quasiparticle spectra is broken. For a cylinder geometry, the zero-energy edge states may appear, but they are localized at one boundary. For the finite-size system with open boundaries, the Majorana bound states emerge only at parts of the system corners. All of the asymmetrical results can be understood well by exploring the pairing order parameter and the anomalous Green's function.