Helical Majorana fermions and flat edge states in the heterostructures of iridates and high-T-C cuprates

Majorana bound states exist inside a core of the half-quantum vortex in spin-triplet superconductors. Despite intense efforts, they have not been discovered in any spin-triplet superconductor candidate materials. After the success of the topological insulator, another route to achieve Majorana fermions has been suggested: heterostructures of s-wave superconductors and the topological insulator or semimetal with strong spin-orbit coupling provide an effective spinless p + ip pairing. This theoretical observation has stimulated experimental searches for Majorana bound states, and further theoretical studies on propagating Majorana fermions beyond bound states. Here we show that high-T-C superconductor-based-heterostructures exhibit both helical Majorana fermions and zero-energy flat edge states. We suggest that an Ir oxide layer of Sr2IrO4 in close proximity to high-T-C cuprates would be a good example to explore these boundary states.