HIGH CRITICAL-TEMPERATURE IN A SUPERLATTICE OF QUANTUM WIRES

Here we report experimental evidence that the high T-C superconductivity in a cuprate perovskite occurs in a superlattice of Josephson coupled quantum wires. We show that this particular heterostructure provides the physical mechanism raising Te from the low temperature range TC<23K to the high temperature range 30K<T-C<150K by amplification of the critical temperature of the homogeneous CuO2 plane by a factor similar to 10. The structure of the high T-C superconducting CuO2 plane in Bi2Sr2CaCu2O8+y (Bi2212) at the mesoscopic level (10-100 Angstrom) has been determined. The superconducting plane is decorated by a plurality of parallel superconducting stripes of width L defined by the domain walls formed by stripes of width W characterized by a short Cu-O(apical) distance and large tilting similar to 10 degrees of the distorted square pyramids. We have measured the width of the domain walls W=11+/-1 Angstrom and of the stripes L=14 +/-1 Angstrom. The critical parameters raising Te are: 1) the Fermi level is near the bottom of the second subband of the stripes, with k(2 gamma)=2 pi/L, formed by the quantum size effect and 2) W is of the order of the superconducting coherence length xi(0).