Fine Effects in the Temperature Dependence of the Thermal Conductivity of Y-123 Cuprates in a “Weak” Pseudogap State

Quasiregular anomalies of the thermal conductivity k of the YBa 2 Cu 3 O 7 − x hole high-temperature superconductor in a pseudogap state, as well as a “giant” anomaly near T C , have been detected for the first time. The temperature anomalies of the carrier density ( n h ) in YBa 2 Cu 3 O 7 − x have been revealed and their correlation with k anomalies has been established. It has been shown that n h ( k ) anomalies of the pseudogap state are due to the step-by-step pairing of charge carriers into positively charged bosons. The correlation of n h ( k ) anomalies near T C with the topological conversion of a part of the Fermi surface, on one hand, and with the structure anomaly, on the other hand, has been established.