Evolution of the metal–insulator transition in oxygen nonstoichiometric YBa2Cu3O7−δ single crystals under pressure
The influence of high hydrostatic pressure on the conductivity in the ab-plane of high-temperature superconductors of the YBa2Cu3O7−δ system is investigated. It was found that, an increase in the oxygen deficiency in YBa2Cu3O7−δ single crystals leads to increased localization effects. It is determined that the metal–insulator type transition always precedes the superconducting transition. The increase in pressure, leads to a significant displacement of the point of the metal–insulator transition to the region of high temperatures.