Andreev conductance in the d plus id′-wave superconducting states of graphene

We show that effective superconducting orders generally emerge at low energy in the superconducting state of graphene with conventionally defined pairing symmetry. We study a particular interesting example, the d(x2-y2)+id(xy)(') spin singlet pairing state in graphene which can be generated by electronic correlation. We find that effectively the d+id(')-wave state is a state with mixed s-wave and exotic p+ip-wave pairing orders at low energy. This remarkable property leads to distinctive superconducting gap functions and behavior of the Andreev conductance spectra through a normal/superconducting graphene structure.