  The coexistence of neutron-neutron (n-n), proton-proton (p-p), and
neutron-proton (n-p) pairings is investigated by adopting an effective
density-dependent contact pairing potential. These three types of pairings can
coexist only if the n-p pairing is stronger than the n-n and p-p pairings for
isospin asymmetric nuclear matter. In addition, the existence of n-n and p-p
pairs might enhance n-p pairings in asymmetric nuclear matter when the n-p
pairing strength is significantly stronger than the n-n and p-p ones.
Conversely, the n-p pairing is reduced by the n-n and p-p pairs when the n-p
pairing interaction approaches n-n and p-p pairings.
