͑BaCuO 2 ͒ 2 /͑CaCuO 2 ͒ n superconducting superlattices have been grown by pulsed laser deposition for n ranging from 1 to 6. The critical temperature was found to depend strongly on the growth conditions. A maximum T c value of about 80 K ͑zero resistance temperature͒ was found for superlattices grown at high oxygen pressure ( P O 2 Ӎ0.8 mbar) and relatively high temperature (T g Ӎ600°C). The dependence of T c on the number n of CaCuO 2 layers ͑for superlattices grown exactly in the same conditions͒ was investigated. T c versus n showed the expected behavior with a maximum T c value of 80 K for nϭ2 -3. However, such value is somewhat lower than that expected for a cuprate structure containing 3-4 CuO 2 planes and having an optimum carrier concentration. Two possible explanations for this effect can be envisaged. The first one deals with the chemistry of the ''charge reservoir'' block, the second one with the special role of interelectron interaction in these highly disordered artificial structures. Finally, it is shown that, taking into account the degree of disorder, a shift of T c of about 20 K relative to the bulk value T c 0 , consistent with the microscopic parameters of these materials, can be foreseen. ͓S0163-1829͑98͒51334-3͔Phys. ͑to be published͒. 18 M. Randeria ͑unpublished͒.
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R8928PRB 58 G. BALESTRINO et al.