Normal State Resistivity of YBa_2Cu_3O_(7-δ) /PrBa_2Cu_(2.8)Ga_(0.2)O_(7-δ) c-axis Superlattices: Evidence for an Underdoping Effect of YBa_2Cu_3O_(7-δ)

摘要

We measured the ab-plane resistivity of c-axis YBa_2Cu_3O_(7-δ) /PrBa_2Cu_(2.8)Ga_(0.2)O_7 superlattices grown by pulsed laser deposition, from T_c to 325 K. The normalstate resistivity and the fluctuation regime above T_c were studied for different thickness of YBa_2Cu_3O_(7-δ) and PrBa_2Cu_(2.8)Ga_(0.2)O_(7-δ) in the superlattice period. As the concentration of PrBa_2Cu_(2.8)Ga_(0.2)O_(7-δ) is raised, the T_c decreases and the resistivity increases. Evidence is given for an underdoping effect in the YBa_2Cu_3O_(7-δ) layers and our measurements are compared to similar measurements on oxygen-deficient YBa_2Cu_3O_(7-δ) thin films, grown on the same equipment. They are also compared to measurements on YBa_2Cu_(3-x)Co_xO_(7-δ) single crystals made by other groups. We present here the different measurements and investigate the mechanisms that could be held responsible for this depletion in charge carriers.