Topological phase transition induced by Zeeman field in topological insulator/superconductor heterostructure

We investigate a topological insulator -- superconductor heterostructure with an Abrikosov vortex in a magnetic field. Large Zeeman field causes a topological phase transition in the system. We found that a Majorana fermion exists at the vortex core in the phase with zero first Chern number and does not exist at the phase with non-trivial first Chern number. This result is supported by the index theorem. This system provides an example in which a Majorana fermion emerges in a system with zero first Chern number.