Gap distribution and multigap-coupling in highT c 's

Gap coupling interaction is a necessary consequence if a superconducting system has a gap distribution, as found for the high-T _c oxocuprates, since the interaction has to result in a single critical temperatureT _c . This paper shows with the help of BCS gap-coupling equations and values of gap distribution, including gap weights from experiments, thatT _c values as observed are easily achievable with reasonable diagonal and off-diagonal coupling coefficients. Of course our phenomenologically derived coupling coefficients have to be verified from purely theoretical grounds. Most importantly, it is found that the highest gap contributes dominantly toT _c in spite of its low weight. Predictions for a point-contact tunneling spectroscopy are made.