MULTIGAP STRUCTURE IN THE CUPRATES

Some of the cuprate superconductors, especially Y1Ba2Cu3O7 are characterized by the presence of different overlapping energy bands. The short coherence length requires the introduction of a multigap structure for these materials. General properties of the two-gap model are described and several new results are presented. The model is characterized by several coupling constants and it requires an unconventional analysis particularly if we are concerned with the relation between the values of the gaps and the strength of the coupling. We find generally that one gap must be karger and the other smaller than in the single gap picture. Furthermore, strong coupling effects will decrease the relative difference in the values of the two gaps. We have applied these ideas to explain the NMR data as well as the anomalous critical temperature and magnetic field behavior of PrxY1-xBa2Cu3O7. © 1990.