Hg-Based Superconducting Cuprates: High Tc and Pseudo Spin-Gap
  A brief review of microscopic studies of high-Tc superconductors HgBa2CuO4+d and HgBa2CaCu2O6+d is presented. The topics concerned are the pseudo spin-gap, the antiferromagnetic spin fluctuations near the quantum critical point, and the mechanism of the high Tc via NMR. The crystal structure with the flat CuO2 plane, two-dimensional electrical resistivity, Cu NQR, NMR experimental results are discussed. 
Y. Itoh and T. Machi