Transport measurements in YBa2Cu3O7-delta/PrBa2Cu3-xGaxO7-delta superlattices: experimental evidence for underdoping

The normal state resistivity of YBa2Cu3O7-delta/PrBa2Cu3-xGaxO7 (x = 0.2) s uperlattices grown by Pulsed Laser Deposition is studied as a function of t emperature from T-c to 325 K. The respective YBa2Cu3O7-delta (YBCO) and PrB a2Cu3-xGaxO7-delta (PBCGO) thickness are varied. A decrease and a broadenin g of T-c as well as an increase of rho(100 K) are observed with increasing PrBa2C3-xGaxO7-delta content. For temperatures lower than 200 K, the PrBa2C u3-xGaxO7-delta does not contribute to the conductivity of the superlattice , which shows an analogy with the one for underdoped compounds. The data ar e compared to similar measurements on oxygen-deficient YBCO thin films and YBa2Cu3-xCoxO7-delta single crystals: this allows to conclude to a underdop ing effect of the superconducting CuO2 planes in the superlattices, probabl y due to charge transfer from the YBCO layers to the PrBa2Cu3-xGaxO7 layers . (C) 1999 Elsevier Science B.V. All rights reserved.