Structural distortions and extension of superconducting region in the T-c-p phase diagram of HgBa2CuO4+delta

In monolayer Hg-based high-T-c materials, the T-c-p phase diagram follows a relationship different from that followed by many other high-T-c materials . It has been observed that an extension of the superconducting region take s place in the overdoped region and a buckling of the Cu-O-Cu bond on the c opper-oxide plane is introduced when overdoped materials are made by substi tuting thallium in the place of mercury. Connection between this buckling a nd the extension of superconducting region is investigated, and an interpre tation of the extension proposed in the light of a quantum paraelectric mod el. (C) 2001 Elsevier Science B.V. All rights reserved.