Paramagnetically induced gapful topological superconductors

We propose a generic scenario for realizing gapful topological superconductors (TSCs) from gapless spin-singlet superconductors (SCs). Noncentrosymmetric nodal SCs in two dimension are shown to be gapful under a Zeeman field, as a result of the cooperation of inversion-symmetry breaking and time-reversal-symmetry breaking. In particular, non-s-wave SCs acquire a large excitation gap. Such paramagnetically-induced gapful SCs may be classified into TSCs in the symmetry class D specified by the Chern number. We show nontrivial Chern numbers over a wide parameter range for spin-singlet SCs. A variety of the paramagnetically-induced gapful TSCs are demonstrated, including D+p-wave TSC, extended S+p-wave TSC, p+D+f-wave TSC, and s+P-wave TSC. Natural extension toward three-dimensional Weyl SCs is also discussed.