Pseudogap state and superconducting state in high-T-c cuprates: anomalous properties in the observed quantities

We theoretically investigate the anomalous properties of under-doped high-T -c cuprates. both in the normal state and in the superconducting state. We especially pay attention to the pseudogap phenomena in the normal state and their relationship with the superconductivity. We have shown in our previo us paper that the pseudogap phenomena are naturally understood as a precurs or of the strong coupling superconductivity. We extend our scenario to the superconducting state and discuss the close relationship between the pseudo gap state and the superconducting state. The calculation is carried out by using the self consistent T-matrix approximation. Once the superconducting phase transition occurrs the superconducting fluctuations are suppressed, a nd the order parameter rapidly grows. With the growth of the order paramete r. the gap structure, which is broad in the pseudogap state, becomes sharp. This transition is continuous but rapid. The characteristic scale of the g ap is the same, as is directly observed in the spectroscopic measurements. The characteristic features also appear in the several other measurements. We further carry out the definite calculation on the NMR and transport, whi ch show the pseudogap anomaly in the normal state. We investigate their beh aviors both in the pseudogap state and in the superconducting stare. (C) 20 00 Elsevier Science Ltd. All rights reserved.