Hydrostatic pressure effect on the pseudogap in Y0.77Pr0.23Ba2Cu3O7–δ single crystals

Abstract

Significant efforts have been made to elucidate the properties of high-temperature superconductors (HTSCs) using hydrostatic pressure (HP). We studied the changes of resistivity ρ(T), superconduting transition tempetature Tc, fluctuation conductivity σ′(T), and pseudogap Δ*(T) of Y1−xPrxBa2Cu3O7−δ (YPrBCO) (x = 0.23) single crystal under HP up to ∼1.1 GPa. Defects created by magnetic inclusions of PrBa2Cu3O7–δ (PrBCO) were found to play a significant role in the behavior of the sample. The largest decrease in ρ(T) was found depending on HP at a rate of d ln ρ(100 K)/dP = –(29 ± 0.2) %⋅GPa−1. This indicates that the mechanisms of the influence of HP on the ρ(T) and Tc of YPrBCO and YBa2Cu3O7–δ single crystals are different. From the analysis of the pseudogap, it was revealed that the mechanism of the interaction of charge carriers with magnetic PrBCO impurities changes three times with increasing HP. Relatively low HP, up to ∼0.5 GPa, promotes the formation of defects caused by PrBCO magnetic inclusions. Starting from 0.6 GPa, the HP neutralizes the influence of magnetic impurities, and the magnetic maximum on Δ*(T) disappears. Above ∼1.0 GPa, HP aligns the magnetic moments of PrBCO, and the magnetic maximum reappears on Δ*(T), more pronounced than at P = 0. Comparison with the Peters–Bauer theory showed that the local pair density in HTSC does indeed increase with increasing pressure.