The High Pressure Synthesis and Properties of Apical Oxygen Doped High Tc Superconductors

The (Sr,Ca)n+1CunO2n(Cl,O)2 superconducting homologous series have been briefly introduced. The emphasis is on the special charge reservoir block of the oxyhalide high Tc superconductror (HTSC), which consists of the halide layer instead of the routine oxide layer. Consequently the apical oxygen related to the p-type HTSC is missed in the compound whereas the apical chlorine bridges the conducting layer and the charge reservoir. In the context a novel hole doping mechanism named apical oxygen doping was introduced through partially substituting oxygen for chlorine. This chemical doping leads to an 80 K superconducting transition in the high pressure synthesized double layered (Sr,Ca)3Cu2O4(Cl,O)2 oxyhalide. Not only the high Tc, the oxyhalide cuprate superconductor also demonstrates the comparable physical properties to those of the full oxide HTSC, indicating the promising prospects to develop new high Tc oxyhalide superconductors.