  Pairing in superconductors occurs in a variety of channels and can be
produced by various mechanisms. Here, we show that, in the presence of strong
correlations, a novel singlet-pair superconducting phase can occur in ladder
geometries with the fermions in the pairs residing on different sides of a Mott
insulating stripe. The antiferromagnet correlations in the Mott stripe provide
the pairing "glue" in such a phase. We study, using the density matrix
renormalization group method, the ground state of four-leg t-J ladders with
Mott insulating stripes in the inner two legs. Pairing and superconductivity
are revealed by the presence of negative binding energies and by algebraically
decaying interleg singlet-pair correlations, respectively.
