Fractional vortices and Ising superconductivity in multiband superconductors

Inspired by the recent experiments in monolayer iron-based superconductors, we theoretically investigate properties of a two-dimensional multiband superconductor, focusing on two aspects. First, for vortex bound states, the spatial anisotropy and positions of electron density peaks are associated with interband couplings. Second, even with inversion symmetry, there allows a Ising-type spin-orbit coupling, leading to the enhanced in-plane upper critical field.