Complete zero-energy flat bands of surface states in fully gapped chiral noncentrosymmetric superconductors

Flat bands of surface states in noncentrosymmetric superconductors accompanied by a full gap in the bulk would be an alternative route to a strongly interacting two-dimensional Fermi system. They could provide a robust platform for quantum computation. Here, the authors explore a way to stabilize such bands in the entire surface Brillouin zone by introducing an additional spin-rotation symmetry that forces the direction of the spin-orbit-coupling vector not to depend on the momentum component, normal to the surface.