  We consider an interface separating the Moore-Read state and Halperin 331
state in a half filled Landau level, which can be realized in a double quantum
well system with varying inter-well tunneling and/or interaction strength. We
find in the presence of electron tunneling and strong Coulomb interaction
across the interface, all charge modes localize and the only propagating mode
left is a chiral Majorana fermion mode. Methods to probe this neutral mode are
proposed. Quantum phase transition between the Moore-Read and Halperin 331
states is described by a network of such Majorana fermion modes. In addition to
a direct transition, they may also be separated by a phase in which the
Majorana fermions are delocalized, realizing an incompressible state which
exhibits quantum Hall charge transport and bulk heat conduction.
