Surface density of states and topological edge states in noncentrosymmetric superconductors

We study an Andreev bound state (ABS) and the surface density of state (SDOS) of a noncentrosymmetric superconductor where spin-singlet d-wave pairing mixes with spin-triplet p (or $f)$-wave pairing by spin-orbit coupling. For dxy+p-wave pairing, the ABS appears as a zero-energy state. The present ABS is a Majorana edge mode preserving the time-reversal symmetry. We calculate the topological invariant and discuss the relevance to a single Majorana edge mode. In the presence of the Majorana edge mode, the SDOS depends strongly on the direction of the Zeeman field.