Tuning of the Fermi level at the second subband of a superlattice of quantum wires in the CuO2 plane: A possible mechanism to raise the critical temperature

The structure of the stripes in Bi2Sr2CaCu2O8 + y superconductor has been refined by polarized Cu K-edge extended X-ray absorption fine structure (EXAFS). The distribution of Cu-O (planar) distances range from 1.87 Å to 1.96 Å. The results show that the in-plane CuO2 lattice distortions in the 1D modulation are large enough to form a potential barrier of width W between the stripes of undistorted CuO2 lattice of width L = 15 ± 0.5 Å. The calculations show that the maximum of the density of states formed by the second subband is tuned to the Fermi level.