Modulated structure and superconductivity in 2D electron-hole lattice system

The close relationship between modulated structures and superconductivity in high-Tc oxide superconductors is explained by using a two-dimensional (2D) electron-hole lattice. The 2D electron-hole lattice is constructed on the crystal surface or between adjacent layers by neutralizing polarization charges caused by a local polarization along with c-axis. The local polarization in the oxide superconductors is often accompanied by a modulated structure, with the modulation period corresponding to the length of one side of the 2D electron-hole lattice, D. Assuming that the Cooper pairs can be formed through the exchange of the open-quotes phononsclose quotes of the 2D electron-hole lattice oscillation, the authors show that both the optimum carrier density and the peak value of the transition temperature are approximately proportional to D-3/2 and D-2, respectively, and that for a typical value of D ∼ 15 angstrom, they are estimated to be on the order of 1014/cm2 and 100 K, respectively