Andreev peaks and massive magnons in cuprate superconductor-normal-superconductor junctions

The projected SO(5) theory [pSO(5)] is used to resolve the puzzle of two di stinct energy gaps in high T-c superconductor-normal-superconductor junctio ns. Counter to the conventional theory of multiple Andreev reflections (MAR ), the differential resistance peaks are associated with the antiferromagne tic resonance observed in neutron scattering, and not with Cooper pair brea king. The pSO(5) and MAR theories differ by the expected tunneling charges at the peaks. We propose that shot noise experiments could discriminate aga inst the conventional interpretation.